Filed Pursuant to Rule 497
Registration No. 333-214767

PROSPECTUS SUPPLEMENT

(To prospectus dated September 7, 2017)

Up to 12,000,000 Shares

Common Stock

We have entered into an equity distribution agreement, dated September 8, 2017, or the Equity Distribution Agreement, with JMP Securities LLC, or JMP Securities, relating to the shares of common stock offered by this prospectus supplement and the accompanying prospectus. Our common stock is listed on the New York Stock Exchange, or NYSE, under the trading symbol “HTGC.” The last reported sale price on the NYSE on May 4, 2018 was $12.31 per share. The net asset value per share of our common stock at March 31, 2018 (the last date prior to the date of this prospectus supplement on which we determined net asset value) was $9.72.

We are an internally managed, non-diversified, closed-end investment company that has elected to be regulated as a business development company under the Investment Company Act of 1940, as amended, or the 1940 Act. Our investment objective is to maximize our portfolio total return by generating current income from our debt investments and capital appreciation from our warrant and equity-related investments.

The Equity Distribution Agreement provides that we may offer and sell up to 12,000,000 shares of our common stock from time to time through JMP Securities, as our sales agent. Sales of our common stock, if any, under this prospectus supplement and the accompanying prospectus may be made in negotiated transactions or transactions that are deemed to be “at the market,” as defined in Rule 415 under the Securities Act of 1933, as amended, or the Securities Act, including sales made directly on the NYSE or similar securities exchange or sales made to or through a market maker other than on an exchange, at prices related to the prevailing market prices or at negotiated prices. As of the date of this prospectus supplement, we have sold approximately 2.8 million shares of our common stock under the Equity Distribution Agreement.

JMP Securities will receive a commission from us to be negotiated from time to time, but in no event in excess of 2.0% of the gross sales price of any shares of our common stock sold through JMP Securities under the Equity Distribution Agreement. JMP Securities is not required to sell any specific number or dollar amount of common stock, but will use its commercially reasonable efforts consistent with its sales and trading practices to sell the shares of our common stock offered by this prospectus supplement and the accompanying prospectus. See “Plan of Distribution” beginning on page S-27 of this prospectus supplement. The sales price per share of our common stock offered by this prospectus supplement and the accompanying prospectus, less JMP Securities’ commission, will not be less than the net asset value per share of our common stock at the time of such sale.

Please read this prospectus supplement, and the accompanying prospectus, before investing, and keep it for future reference. The prospectus supplement and the accompanying prospectus contain important information about us that a prospective investor should know before investing in our common stock. We file annual, quarterly and current reports, proxy statements and other information about us with the Securities and Exchange Commission, or the SEC. This information is available free of charge by contacting us at 400 Hamilton Avenue, Suite 310, Palo Alto, California 94301, or by telephone by calling collect at (650) 289-3060 or on our website at www.htgc.com. The information on our website is not incorporated by reference into this prospectus or the accompanying prospectus. The SEC also maintains a website at www.sec.gov that contains such information.

An investment in our common stock involves risks, including the risk of a total loss of investment. In addition, the companies in which we invest are subject to special risks. See the “Supplementary Risk Factors” section beginning on page S-15 of this prospectus supplement and the “Risk Factors” section beginning page 14 of the accompanying prospectus to read about risks that you should consider before investing in our common stock, including the risk of leverage.

Neither the SEC nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

JMP Securities

The date of this prospectus supplement is May 9, 2018.

You should rely only on the information contained in this prospectus supplement and the accompanying prospectus. We have not, and JMP Securities has not, authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We are not, and JMP Securities is not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information contained in this prospectus supplement and the accompanying prospectus is accurate only as of the date on the front cover of this prospectus supplement and the accompanying prospectus, as applicable. Our business, financial condition, results of operations and prospects may have changed since that date.

This document is in two parts. The first part is this prospectus supplement, which describes the terms of this offering and also adds to and updates information contained in the accompanying prospectus. The second part is the accompanying prospectus, which gives more general information and disclosure. To the extent the information contained in this prospectus supplement differs from the information contained in the accompanying prospectus, the information in this prospectus supplement shall control. You should read this prospectus supplement and the accompanying prospectus together with the additional information described under the heading, “Available Information” before investing in our common stock.

TABLE OF CONTENTS

Prospectus Supplement

Prospectus

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FEES AND EXPENSES

The following table is intended to assist you in understanding the various costs and expenses that an investor in our common stock will bear directly or indirectly. However, we caution you that some of the percentages indicated in the table below are estimates and may vary. The footnotes to the fee table state which items are estimates. Except where the context suggests otherwise, whenever this prospectus contains a reference to fees or expenses paid by “you” or “us” or that “we” will pay fees or expenses, stockholders will indirectly bear such fees or expenses as investors in Hercules Capital, Inc.

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Example

The following example demonstrates the projected dollar amount of total cumulative expenses that would be incurred over various periods with respect to a hypothetical investment in our common stock. These amounts are based upon our payment of annual operating expenses at the levels set forth in the table above and assume no additional leverage.

The example and the expenses in the tables above should not be considered a representation of our future expenses, and actual expenses may be greater or lesser than those shown. Moreover, while the example assumes, as required by the applicable rules of the SEC, a 5% annual return, our performance will vary and may result in a return greater or lesser than 5%. In addition, while the example assumes reinvestment of all distributions at net asset value (“NAV”), participants in our dividend reinvestment plan may receive shares valued at the market price in effect at that time. This price may be at, above or below NAV. See “Dividend Reinvestment Plan” in the accompanying prospectus for additional information regarding our dividend reinvestment plan.

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FORWARD-LOOKING STATEMENTS

The matters discussed in this prospectus supplement and the accompanying prospectus, as well as in future oral and written statements by management of Hercules Capital, Inc., that are forward-looking statements are based on current management expectations that involve substantial risks and uncertainties which could cause actual results to differ materially from the results expressed in, or implied by, these forward-looking statements. Forward-looking statements relate to future events or our future financial performance. We generally identify forward-looking statements by terminology such as “may,” “will,” “should,” “expects,” “plans,” “anticipates,” “could,” “intends,” “target,” “projects,” “contemplates,” “believes,” “estimates,” “predicts,” “potential” or “continue” or the negative of these terms or other similar expressions. Important assumptions include our ability to originate new investments, achieve certain margins and levels of profitability, the availability of additional capital, and the ability to maintain certain debt to asset ratios. In light of these and other uncertainties, the inclusion of a projection or forward-looking statement in this prospectus supplement and the accompanying prospectus should not be regarded as a representation by us that our plans or objectives will be achieved. The forward-looking statements contained in this prospectus supplement and the accompanying prospectus include statements as to:

For a discussion of factors that could cause our actual results to differ from forward-looking statements contained in this prospectus supplement and the accompanying prospectus, please see the discussion under “Supplementary Risk Factors” beginning on page S-15 of this prospectus supplement and “Risk Factors” beginning on page 14 of the accompanying prospectus. You should not place undue reliance on these forward-looking statements. The forward-looking statements made in this prospectus relate only to events as of the date on which the statements are made. We undertake no obligation to update any forward-looking statement to reflect events or circumstances occurring after the date of this prospectus.

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INDUSTRY AND MARKET DATA

We have compiled certain industry estimates presented in this prospectus supplement and the accompanying prospectus from internally generated information and data. While we believe our estimates are reliable, they have not been verified by any independent sources. The estimates are based on a number of assumptions, including increasing investment in venture capital and private equity-backed companies. Actual results may differ from projections and estimates, and this market may not grow at the rates projected, or at all. If this market fails to grow at projected rates, our business and the market price of our securities, including our common stock, could be materially adversely affected.

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SELECTED CONSOLIDATED FINANCIAL DATA

The selected consolidated financial data should be read in conjunction with “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” “Senior Securities” and the consolidated financial statements and related notes included elsewhere herein. The selected balance sheet data as of the end of fiscal year 2017, 2016, 2015, 2014, and 2013 and the financial statement of operations data for fiscal years 2017, 2016, 2015, 2014, and 2013 has been derived from our audited financial statements, which have been audited by PricewaterhouseCoopers LLP, our independent registered public accounting firm, but not all of which are presented in this prospectus supplement. The historical data are not necessarily indicative of results to be expected for any future period. The selected financial and other data for the three-months ended March 31, 2018 and other quarterly financial information is derived from our unaudited financial statements, but in the opinion of management, reflects all adjustments (consisting only of normal recurring adjustments) that are necessary to present fairly the results of such interim periods. Interim results as of and for the three-months ended March 31, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018.

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The following tables set forth certain quarterly financial information for each of the eight quarters up to and ending December 31, 2017 and the quarter ending March 31, 2018. This information was derived from our unaudited consolidated financial statements. Results for any quarter are not necessarily indicative of results for the full year or for any future quarter.

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SUPPLEMENTARY RISK FACTORS

Investing in our securities may be speculative and involves a high degree of risk. You should consider carefully the risks described below and all other information contained in this prospectus supplement. The risks set forth below are not the only risks we face. Additional risks and uncertainties not presently known to us or not presently deemed material by us may also impair our operations and performance. If any of the following risks occur, our business, financial condition and results of operations could be materially adversely affected. In such case, our NAV and the trading price of our securities could decline, and you may lose all or part of your investment.

Risks Related to our Business Structure

As an internally managed business development company, we are subject to certain restrictions that may adversely affect our business.

As an internally managed business development company, the size and categories of our assets under management is limited, and we are unable to offer as wide a variety of financial products to prospective portfolio companies and sponsors (potentially limiting the size and diversification of our asset base). We therefore may not achieve efficiencies of scale and greater management resources available to externally managed business development companies.

Additionally, as an internally managed business development company, our ability to offer more competitive and flexible compensation structures, such as offering both a profit sharing plan and an equity incentive plan, is subject to the limitations imposed by the 1940 Act, which limits our ability to attract and retain talented investment management professionals. As such, these limitations could inhibit our ability to grow, pursue our business plan and attract and retain professional talent, any or all of which may have a negative impact on our business, financial condition and results of operations.

As an internally managed business development company, we are dependent upon key management personnel for their time availability and for our future success, particularly Manuel A. Henriquez, and if we are not able to hire and retain qualified personnel, or if we lose any member of our senior management team, our ability to implement our business strategy could be significantly harmed.

As an internally managed business development company, our ability to achieve our investment objectives and to make distributions to our stockholders depends upon the performance of our senior management. We depend upon the members of our senior management, particularly Mr. Henriquez, as well as other key personnel for the identification, final selection, structuring, closing and monitoring of our investments. These employees have critical industry experience and relationships on which we rely to implement our business plan. If we lose the services of Mr. Henriquez or any senior management members, we may not be able to operate the business as we expect, and our ability to compete could be harmed, which could cause our operating results to suffer. Furthermore, we do not have an employment agreement with Mr. Henriquez or our senior management that restricts them from creating new investment vehicles subject to compliance with applicable law. We believe our future success will depend, in part, on our ability to identify, attract and retain sufficient numbers of highly skilled employees. If we do not succeed in identifying, attracting and retaining such personnel, we may not be able to operate our business as we expect. In connection with our recruiting, branding and marketing efforts, we may, among other things, make charitable contributions in amounts we believe to be immaterial. We believe that many of these contributions help us raise our profile in the communities and benefit us in attracting and retaining talent and investment opportunities.

As an internally managed business development company, our compensation structure is determined and set by our Board of Directors. This structure currently includes salary and bonus and incentive compensation, which is issued through grants and subsequent vesting of restricted stock. We are not generally permitted by the 1940 Act to

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employ an incentive compensation structure that directly ties performance of our investment portfolio and results of operations to compensation owing to our granting of restricted stock as incentive compensation.

Members of our senior management may receive offers of more flexible and attractive compensation arrangements from other companies, particularly from investment advisers to externally managed business development companies that are not subject to the same limitations on incentive-based compensation that we, as an internally managed business development company are subject to. We do not currently have agreements with certain members of our senior management that prohibit them from leaving and competing with our business and certain States limit our ability to have such agreements. In addition, the evaluation of alternative management structures discussed above may lead to changes in our management structure. A departure by one or more members of our senior management could have a negative impact on our business, financial condition and results of operations.

Because we have substantial indebtedness, there could be increased risk in investing in our company.

Lenders have fixed dollar claims on our assets that are superior to the claims of stockholders, and we have granted, and may in the future grant, lenders a security interest in our assets in connection with borrowings. In the case of a liquidation event, those lenders would receive proceeds before our stockholders. In addition, borrowings, also known as leverage, magnify the potential for gain or loss on amounts invested and, therefore, increase the risks associated with investing in our securities. Leverage is generally considered a speculative investment technique. If the value of our assets increases, then leverage would cause the NAV attributable to our common stock to increase more than it otherwise would have had we not leveraged. Conversely, if the value of our assets decreases, leverage would cause the NAV attributable to our common stock to decline more than it otherwise would have had we not used leverage. Similarly, any increase in our revenue in excess of interest expense on our borrowed funds would cause our net income to increase more than it would without the leverage. Any decrease in our revenue would cause our net income to decline more than it would have had we not borrowed funds and could negatively affect our ability to make distributions on common stock. Our ability to service any debt that we incur will depend largely on our financial performance and will be subject to prevailing economic conditions and competitive pressures. We and, indirectly, our stockholders will bear the cost associated with our leverage activity. If we are not able to service our substantial indebtedness, our business could be harmed materially.

Our Credit Facilities, our 2022 Notes, our 2024 Notes, our 2021 Asset-Backed Notes, our 2022 Convertible Notes, and our 2025 Notes (each as defined herein) contain financial and operating covenants that could restrict our business activities, including our ability to declare dividend distributions if we default under certain provisions.

As of March 31, 2018, we had no borrowings outstanding under the $120.0 million revolving senior credit facility with Wells Fargo Capital Finance, LLC (the “Wells Facility”) and the $75.0 million revolving senior secured credit facility with MUFG Union Bank, N.A. (the “Union Bank Facility,” and together with the Wells Facility, the “Credit Facilities”). In addition, as of March 31, 2018, we had approximately $190.2 million of indebtedness outstanding incurred by our SBIC subsidiaries, approximately $150.0 million in aggregate principal amount of 4.625% notes due 2022 (the “2022 Notes”), approximately $183.5 million in aggregate principal amount of 2024 Notes, approximately $33.6 million in aggregate principal amount of fixed-rate asset-backed notes (the “2021 Asset-Backed Notes”) in connection with our $237.4 million debt securitization (the “2014 Debt Securitization”) and approximately $230.0 million in aggregate principal amount of 4.375% convertible notes due 2022 (the “2022 Convertible Notes”). Additionally, subsequent to March 31, 2018, we had approximately $75.0 million in aggregate principal amount of 2025 Notes.

There can be no assurance that we will be successful in obtaining any additional debt capital on terms acceptable to us or at all. If we are unable to obtain debt capital, then our equity investors will not benefit from the potential for increased returns on equity resulting from leverage to the extent that our investment strategy is successful and we may be limited in our ability to make new commitments or fundings to our portfolio companies.

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As a business development company, under the 1940 Act, generally, we are not permitted to incur indebtedness unless immediately after such borrowing we have an asset coverage for total borrowings of at least 200% (i.e., the amount of debt may not exceed 50% of the value of our assets). In addition, we may not be permitted to declare any cash distribution on our outstanding common shares, or purchase any such shares, unless, at the time of such declaration or purchase, we have asset coverage of at least 200% after deducting the amount of such distribution or purchase price. If this ratio declines below 200%, we may not be able to incur additional debt and may need to sell a portion of our investments to repay some debt when it is disadvantageous to do so, and we may not be able to make distributions. The Small Business Credit Availability Act, which was signed into law in March 2018, modifies this section of the 1940 Act and decreases this percentage from 200% to 150% (subject to either stockholder approval or approval of both a majority of the board of directors and a majority of directors who are not interested persons). As a result of this new law, we may be able to incur additional indebtedness subject to relevant approval and disclosure requirements and, therefore, your risk of an investment in us may increase. Rating agencies may also decide to review our credit ratings and those of other business development companies in light of this new law as well as any corresponding changes to asset coverage ratios and consider downgrading such ratings, including a downgrade from an investment grade rating to a non-investment grade rating. Such a downgrade in our credit ratings may adversely affect our securities. See “Risk Factors—Risks Related to Our Securities—A downgrade, suspension or withdrawal of the credit rating assigned by a rating agency to us or our debt securities, if any, or change in the debt markets could cause the liquidity or market value of our debt securities to decline significantly” in the accompanying prospectus.

As of March 31, 2018, our asset coverage ratio under our regulatory requirements as a business development company was 238.2% excluding our SBIC debentures as a result of our exemptive order from the SEC that allows us to exclude all SBA leverage from our asset coverage ratio and was 204.8% when including all SBA leverage.

Based on assumed leverage equal to 95.0% of our net assets as of March 31, 2018, our investment portfolio would have been required to experience an annual return of at least 2.6% to cover annual interest payments on our additional indebtedness.

Illustration. The following table illustrates the effect of leverage on returns from an investment in our common stock assuming various annual returns, net of expenses. The calculations in the table below are hypothetical and actual returns may be higher or lower than those appearing below.

Acquisitions or investments that we may pursue could be unsuccessful, consume significant resources and require the incurrence of additional indebtedness.

We regularly consider acquisitions and investments that complement our existing business. These possible acquisitions and investments involve or may involve significant cash expenditures, debt incurrence, operating losses and expenses that could have a material effect on our financial condition and operating results.

In particular, if we incur additional debt, our liquidity and financial stability could be impaired as a result of using a significant portion of available cash or borrowing capacity to finance an acquisition. Moreover, we may face an increase in interest expense or financial leverage if additional debt is incurred to finance an acquisition,

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which may, among other things, adversely affect our various financial ratios and our compliance with the conditions of our existing indebtedness. In addition, such additional indebtedness may be secured by liens on our assets.

Acquisitions involve numerous other risks, including:

To the extent we pursue an acquisition that causes us to incur unexpected costs or that fails to generate expected returns, our financial position, results of operations and cash flows may be adversely affected, and our ability to service indebtedness, including our outstanding notes, may be negatively impacted.

In addition, we may fail in our pursuit of an acquisition and, instead, one of our competitors may successfully obtain the target and deprive us of an important opportunity and allow them to grow larger giving them the ability to have a lower cost of capital and competitive advantage in the market (including by being able to offer better pricing and larger loans) and, as a larger company, potentially giving them more valuable equity currency to do other transactions.

The Wells Facility and the Union Bank Facility mature in August 2019 and May 2020, respectively, and any inability to renew, extend or replace our Credit Facilities could adversely impact our liquidity and ability to find new investments or maintain distributions to our stockholders.

As of March 31, 2018, we had two available secured credit facilities, the Wells Facility and the Union Bank Facility, which mature in August 2019 and May 2020, respectively. There can be no assurance that we will be able to renew, extend or replace our Credit Facilities upon maturity on terms that are favorable to us, if at all. Our ability to renew, extend or replace the Credit Facility will be constrained by then-current economic conditions affecting the credit markets. In the event that we are not able to renew, extend or replace either Credit Facility at the time of its maturity, this could have a material adverse effect on our liquidity and ability to fund new investments, our ability to make distributions to our stockholders and our ability to qualify as a RIC.

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Regulations governing our operations as a business development company may affect our ability to, and the manner in which, we raise additional capital, which may expose us to risks.

Our business will require a substantial amount of capital. We may acquire additional capital from the issuance of senior securities, including borrowings, securitization transactions or other indebtedness, or the issuance of additional shares of our common stock. However, we may not be able to raise additional capital in the future on favorable terms or at all. We may issue debt securities, other evidences of indebtedness or preferred stock, and we may borrow money from banks or other financial institutions, which we refer to collectively as “senior securities,” up to the maximum amount permitted by the 1940 Act. Under the 1940 Act, we are not permitted to incur indebtedness unless immediately after such borrowing we have an asset coverage for total borrowings of at least 200% (i.e., the amount of debt may not exceed 50% of the value of our assets). In addition, we may not be permitted to declare any cash distribution on our outstanding common shares, or purchase any such shares, unless, at the time of such declaration or purchase, we have asset coverage of at least 200% after deducting the amount of such distribution or purchase price. Our ability to pay distributions or issue additional senior securities would be restricted if our asset coverage ratio were not at least 200%. The Small Business Credit Availability Act, which was signed into law in March 2018, modifies this section of the 1940 Act and decreases this percentage from 200% to 150% (subject to either stockholder approval or approval of both a majority of the board of directors and a majority of directors who are not interested persons). As a result of this new law, we may be able to incur additional indebtedness subject to relevant approval and disclosure requirements and, therefore, your risk of an investment in us may increase. Rating agencies may also decide to review our credit ratings and those of other business development companies in light of this new law as well as any corresponding changes to asset coverage ratios and consider downgrading such ratings, including a downgrade from an investment grade rating to a non-investment grade rating. Such a downgrade in our credit ratings may adversely affect our other securities. See “Risk Factors—Risks Related to Our Securities—A downgrade, suspension or withdrawal of the credit rating assigned by a rating agency to us or our debt securities, if any, or change in the debt markets could cause the liquidity or market value of our debt securities to decline significantly” in the accompanying prospectus.

If the value of our assets declines, we may be unable to satisfy this test. If that happens, we may be required to liquidate a portion of our investments and repay a portion of our indebtedness at a time when such transaction may be disadvantageous. As a result of issuing senior securities, we would also be exposed to risks associated with leverage, including an increased risk of loss. If we issue preferred stock, the preferred stock would rank “senior” to common stock in our capital structure, preferred stockholders would have separate voting rights and might have rights, preferences, or privileges more favorable than those of our common stockholders and the issuance of preferred stock could have the effect of delaying, deferring, or preventing a transaction or a change of control that might involve a premium price for holders of our common stock or otherwise be in your best interest. It is likely that any senior securities or other indebtedness we issue will be governed by an indenture or other instrument containing covenants restricting our operating flexibility. Additionally, some of these securities or other indebtedness may be rated by rating agencies, and in obtaining a rating for such securities and other indebtedness, we may be required to abide by operating and investment guidelines that further restrict operating and financial flexibility.

To the extent that we are constrained in our ability to issue debt or other senior securities, we will depend on issuances of common stock to finance operations. Other than in certain limited situations such as rights offerings, as a business development company, we are generally not able to issue our common stock at a price below NAV without first obtaining required approvals from our stockholders and our independent directors. If we raise additional funds by issuing more common stock or senior securities convertible into, or exchangeable for, our common stock, then the percentage ownership of our stockholders at that time will decrease, and you might experience dilution. Moreover, we can offer no assurance that we will be able to issue and sell additional equity securities in the future, on favorable terms or at all.

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FATCA withholding may apply to payments made to certain foreign entities.

The Foreign Account Tax Compliance Act provisions of the Code and the related Treasury Regulations and other administrative guidance promulgated thereunder (collectively, “FATCA”) generally requires us to withhold U.S. tax (at a 30% rate) on payments of interest and taxable dividends as well as, effective January 1, 2019, redemption proceeds and certain capital gain dividends made to a foreign financial institution or non-financial foreign entity (including such an institution or entity acting as an intermediary) unless the foreign financial institution or non-financial foreign entity complies with certain information reporting, withholding, identification, certification and related requirements imposed by FATCA. Persons located in jurisdictions that have entered into an intergovernmental agreement with the United States to implement FATCA may be subject to different rules. Stockholders may be requested to provide additional information to enable us to determine whether such withholding is required.

Recently passed legislation may allow us to incur additional leverage.

Historically, as a business development company, under the 1940 Act generally we are not permitted to incur indebtedness unless immediately after such borrowing we have an asset coverage for total borrowings of at least 200% (i.e., the amount of debt may not exceed 50% of the value of our assets). The Small Business Credit Availability Act, which was signed into law in March 2018, modifies this section of the 1940 Act and decreases this percentage from 200% to 150% (subject to either stockholder approval or approval of both a majority of the board of directors and a majority of directors who are not interested persons). As a result of this new law, we may be able to incur additional indebtedness subject to relevant approval and disclosure requirements and, therefore, your risk of an investment in us may increase. Rating agencies may also decide to review our credit ratings and those of other business development companies in light of this new law as well as any corresponding changes to asset coverage ratios and consider downgrading such ratings, including a downgrade from an investment grade rating to a non-investment grade rating. Such a downgrade in our credit ratings may adversely affect our other securities. See “Risk Factors—Risks Related to Our Securities—A downgrade, suspension or withdrawal of the credit rating assigned by a rating agency to us or our debt securities, if any, or change in the debt markets could cause the liquidity or market value of our debt securities to decline significantly” in the accompanying prospectus.

Significant U.S. federal tax legislation was recently enacted and the impact of this new legislation on us and on entities in which we may invest is uncertain.

Significant U.S. federal tax reform legislation was recently enacted that, among many other changes, permanently reduces the maximum federal corporate income tax rate, reduces the maximum individual income tax rate (effective for taxable years 2018 through 2025), restricts the deductibility of business interest expense, changes the rules regarding the calculation of net operating loss deductions that may be used to offset taxable income, and, under certain circumstances, requires accrual method taxpayers to recognize income for U.S. federal income tax purposes no later than the income is taken into account as revenue in an applicable financial statement. The new legislation also makes extensive changes to the U.S. international tax system. The impact of this new legislation on us and on entities in which we may invest is uncertain. Prospective investors are urged to consult their tax advisors regarding the effects of the new legislation on an investment in us.

Risks Related to Current Economic and Market Conditions

Capital markets may experience periods of disruption and instability and we cannot predict when these conditions will occur. Such market conditions could materially and adversely affect debt and equity capital markets in the United States and abroad, which could have a negative impact on our business, financial condition and results of operations.

The global capital markets have experienced a period of disruption as evidenced by a lack of liquidity in the debt capital markets, write-offs in the financial services sector, the re-pricing of credit risk and the failure of

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certain major financial institutions. While the capital markets have improved, these conditions could deteriorate again in the future. During such market disruptions, we may have difficulty raising debt or equity capital, especially as a result of regulatory constraints.

Market conditions may in the future make it difficult to extend the maturity of or refinance our existing indebtedness and any failure to do so could have a material adverse effect on our business. The illiquidity of our investments may make it difficult for us to sell such investments if required. As a result, we may realize significantly less than the value at which we have recorded our investments. In addition, significant changes in the capital markets, including the disruption and volatility, have had, and may in the future have, a negative effect on the valuations of our investments and on the potential for liquidity events involving our investments. An inability to raise capital, and any required sale of our investments for liquidity purposes, could have a material adverse impact on our business, financial condition and results of operations.

Various social and political tensions in the United States and around the world, including in the Middle East, Eastern Europe North Korea, and Russia, may continue to contribute to increased market volatility, may have long-term effects on the United States and worldwide financial markets, and may cause further economic uncertainties or deterioration in the United States and worldwide. In addition, uncertainty regarding the United Kingdom referendum decision to leave the European Union (“Brexit”), continuing signs of deteriorating sovereign debt conditions in Europe and an economic slowdown in China create uncertainty that could lead to further disruptions, instability and weakening consumer, corporate and financial confidence. We may in the future have difficulty accessing debt and equity capital markets, and a severe disruption in the global financial markets, deterioration in credit and financing conditions or uncertainty regarding U.S. government spending and deficit levels, Brexit, European sovereign debt, Chinese economic slowdown or other global economic conditions could have a material adverse effect on our business, financial condition and results of operations.

The broader fundamentals of the United States economy remain mixed. In the event that the United States economy contracts, it is likely that the financial results of small to mid-sized companies, like many of our portfolio companies, could experience deterioration or limited growth from current levels, which could ultimately lead to difficulty in meeting their debt service requirements and an increase in defaults. In addition, declines in oil and natural gas prices could adversely affect the credit quality of our debt investments and the underlying operating performance of our equity investments in energy-related businesses. In addition, volatility in the equity markets could impact our portfolio companies’ access to the debt and equity capital markets, which could ultimately limit their ability to grow, satisfy existing financing and other arrangements and impact their ability to perform. Volatility in the equity markets could also impact our ability to liquidate or achieve value from warrants and other equity investments we have in our portfolio companies. Consequently, we can provide no assurance that the performance of certain portfolio companies will not be negatively impacted by economic cycles, industry cycles or other conditions, which could also have a negative impact on our future results.

These market and economic disruptions affect, and these and other similar market and economic disruptions may in the future affect, the U.S. capital markets, which could adversely affect our business and that of our portfolio companies. We cannot predict the duration of the effects related to these or similar events in the future on the United States economy and securities markets or on our investments. We monitor developments and seek to manage our investments in a manner consistent with achieving our investment objective, but there can be no assurance that we will be successful in doing so.

Risks Related to Our Investments

Our financial results could be negatively affected if a significant portfolio investment fails to perform as expected.

Our total investment in companies may be significant individually or in the aggregate. As a result, if a significant investment in one or more companies fails to perform as expected, our financial results could be more negatively affected and the magnitude of the loss could be more significant than if we had made smaller

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investments in more companies. The following table shows the fair value of the totals of investments held in portfolio companies March 31, 2018 that represent greater than 5% of our net assets:

Our financial results could be materially adversely affected if these portfolio companies or any of our other significant portfolio companies encounter financial difficulty and fail to repay their obligations or to perform as expected.

Risks Related to Our Securities

Terms relating to redemption may materially adversely affect your return on any debt securities that we may issue.

If you are holding debt securities issued by the Company and such securities are redeemable at our option, we may choose to redeem your debt securities at times when prevailing interest rates are lower than the interest rate paid on your debt securities. In addition, if you are holding debt securities issued by the Company and such securities are subject to mandatory redemption, we may be required to redeem your debt securities at times when prevailing interest rates are lower than the interest rate paid on your debt securities. In this circumstance, you may not be able to reinvest the redemption proceeds in a comparable security at an effective interest rate as high as your debt securities being redeemed.

On October 24, 2017, our Board of Directors approved a redemption of $75.0 million of the outstanding aggregate principal amount of the 2024 Notes, which were redeemed on November 23, 2017. Further, on February 9, 2018, our Board of Directors approved a redemption of $100.0 million of the remaining outstanding aggregate principal amount of the 2024 Notes, which were redeemed on April 2, 2018. We may redeem the remaining 2024 Notes at any time prior to maturity, the 2022 Notes after September 23, 2022, and the 2025 Notes after April 30, 2021 at a redemption price of 100% of the outstanding principal amount thereof plus accrued and unpaid interest payments. If we choose to redeem the 2022 Notes, the 2024 Notes, or the 2025 Notes when the fair market value of the 2022 Notes, the 2024 Notes, or the 2025 Notes is above par value, you would experience a loss of any potential premium.

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USE OF PROCEEDS

Overview

Sales of our common stock, if any, under this prospectus supplement and the accompanying prospectus may be made in negotiated transactions or transactions that are deemed to be “at the market” as defined in Rule 415 under the Securities Act, including sales made directly on the NYSE or sales made to or through a market maker other than on an exchange. There is no guarantee that there will be any sales of our common stock pursuant to this prospectus supplement and the accompanying prospectus. Actual sales, if any, of our common stock under this prospectus supplement and the accompanying prospectus may be less than as set forth in this paragraph depending on, among other things, the market price of our common stock at the time of any such sale. As a result, the actual net proceeds we receive may be more or less than the amount of net proceeds estimated in this prospectus supplement. Assuming the sale of the remaining 9,231,742 shares of common stock offered under this prospectus supplement and the accompanying prospectus, at the last reported sale price of $12.31 per share for our common stock on the NYSE as of May 4, 2018, we estimate that the net proceeds of this offering will be approximately $111.2 million after deducting the estimated sales commission payable to JMP Securities and our estimated offering expenses.

We intend to use the net proceeds from this offering to fund investments in debt and equity securities in accordance with our investment objectives, to make acquisitions, to retire certain debt obligations and for other general corporate purposes.

We intend to seek to invest the net proceeds received in this offering as promptly as practicable after receipt thereof consistent with our investment objective. We anticipate that substantially all of the net proceeds from any offering of our securities will be used as described above within three to six months, depending on market conditions. We anticipate that the remainder will be used for working capital and general corporate purposes, including potential payments or distributions to shareholders. Pending such uses and investments, we will invest a portion of the net proceeds of this offering primarily in cash, cash equivalents, U.S. government securities or high-quality debt securities maturing in one year or less from the time of investment. Our ability to achieve our investment objectives may be limited to the extent that the net proceeds of this offering, pending full investment, are held in lower yielding short-term instruments.

Status of the Offering

On September 8, 2017, we established an at-the-market, or ATM, program to which this prospectus supplement relates and through which we may sell, from time to time and at our sole discretion up to 12,000,000 shares of our common stock. During the period from September 8, 2017 through the date of this prospectus supplement, approximately 2.8 million shares of common stock have been issued and sold pursuant to the Equity Distribution Agreement and approximately 9.2 million shares of common stock remain available for sale. Gross proceeds raised through the date of this prospectus were approximately $35.0 million based on an average sale price of $12.63 per share, offset by related underwriting fees and offering expenses of approximately $816,000 for net proceeds of approximately $34.2 million.

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PRICE RANGE OF COMMON STOCK

Our common stock is traded on the NYSE under the symbol “HTGC.”

The following table sets forth the range of high and low sales prices of our common stock, the sales price as a percentage of NAV and the distributions declared by us for each fiscal quarter. The stock quotations are interdealer quotations and do not include markups, markdowns or commissions.

The last reported price for our common stock on May 4, 2018 was $12.31 per share.

Shares of business development companies may trade at a market price that is less than the value of the net assets attributable to those shares. The possibility that our shares of common stock will trade at a discount from NAV or at premiums that are unsustainable over the long term are separate and distinct from the risk that our NAV will decrease. At times, our shares of common stock have traded at a premium to NAV and at times our shares of common stock have traded at a discount to the net assets attributable to those shares. It is not possible to predict whether the shares offered hereby will trade at, above, or below NAV.

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RATIO OF EARNINGS TO FIXED CHARGES

The following contains our ratio of earnings to fixed charges for the periods indicated, computed as set forth below. You should read these ratios of earnings to fixed charges in connection with our consolidated financial statements, including the notes to those statements, included in this prospectus supplement:

For purposes of computing the ratios of earnings to fixed charges, earnings represent net increase in stockholders’ equity resulting from operations plus fixed charges. Fixed charges include interest and credit facility fees expense and amortization of debt issuance costs.

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CAPITALIZATION

The Equity Distribution Agreement provides that we may offer and sell up to 12,000,000 shares of our common stock from time to time through JMP Securities, as our sales agent for the offer and sale of such common stock. The table below assumes that we will sell the remaining 9,231,742 shares at a price of $12.31 per share (the last reported sale price per share of our common stock on the NYSE on May 4, 2018) but there is no guarantee that there will be any sales of our common stock pursuant to this prospectus supplement and the accompanying prospectus. Actual sales, if any, of our common stock under this prospectus supplement and the accompanying prospectus may be less than as set forth in the table below. In addition, the price per share of any such sale may be greater or less than $12.31 depending on the market price of our common stock at the time of any such sale. The following table sets forth our capitalization as of March 31, 2018:

This table should be read in conjunction with “Use of Proceeds” in this prospectus supplement and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our financial statements and notes thereto included in the accompanying prospectus. The adjusted information is illustrative only.

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PLAN OF DISTRIBUTION

JMP Securities LLC is acting as our sales agent in connection with the offer and sale of shares of our common stock pursuant to this prospectus supplement and the accompanying prospectus. Upon written instructions from us, JMP Securities LLC will use its commercially reasonable efforts consistent with its sales and trading practices to sell, as our sales agent, our common stock under the terms and subject to the conditions set forth in the Equity Distribution Agreement. We will instruct JMP Securities LLC as to the amount of common stock to be sold by it. We may instruct JMP Securities LLC not to sell common stock if the sales cannot be effected at or above the price designated by us in any instruction. The sales price per share of our common stock offered by this prospectus supplement and the accompanying prospectus, less JMP Securities LLC’s commission, will not be less than the NAV per share of our common stock at the time of such sale. We or JMP Securities LLC may suspend the offering of shares of common stock upon proper notice and subject to other conditions.

Sales of our common stock, if any, under this prospectus supplement and the accompanying prospectus may be made in negotiated transactions or transactions that are deemed to be “at the market,” as defined in Rule 415 under the Securities Act, including sales made directly on the NYSE or similar securities exchange or sales made to or through a market maker other than on an exchange at prices related to the prevailing market prices or at negotiated prices.

JMP Securities LLC will provide written confirmation of a sale to us no later than the opening of the trading day on the NYSE following each trading day in which shares of our common stock are sold under the Equity Distribution Agreement. Each confirmation will include the number of shares of common stock sold on the preceding day, the net proceeds to us and the compensation payable by us to JMP Securities LLC in connection with the sales.

JMP Securities LLC will receive a commission from us to be negotiated from time to time but in no event in excess of 2.0% of the gross sales price of any shares of our common stock sold through JMP Securities LLC under the Equity Distribution Agreement. We estimate that the total expenses for the offering, excluding compensation payable to JMP Securities LLC under the terms of the Equity Distribution Agreement, will be approximately $713,000 assuming all shares are offered under this prospectus supplement (including up to $10,000 in reimbursement of the underwriters’ counsel fees in connection with the review of the terms of the offering by the Financial Industry Regulatory Authority, Inc.).

Settlement for sales of shares of common stock will occur on the second trading day following the date on which such sales are made, or on some other date that is agreed upon by us and JMP Securities LLC in connection with a particular transaction, in return for payment of the net proceeds to us. There is no arrangement for funds to be received in an escrow, trust or similar arrangement.

We will report at least quarterly the number of shares of our common stock sold through JMP Securities LLC under the Equity Distribution Agreement and the net proceeds to us.

In connection with the sale of the common stock on our behalf, JMP Securities LLC may be deemed to be an “underwriter” within the meaning of the Securities Act, and the compensation of JMP Securities LLC may be deemed to be underwriting commissions or discounts. We have agreed to provide indemnification and contribution to JMP Securities LLC against certain civil liabilities, including liabilities under the Securities Act.

The offering of our shares of common stock pursuant to the Equity Distribution Agreement will terminate upon the earlier of (i) the sale of all common stock subject to the Equity Distribution Agreement or (ii) the termination of the Equity Distribution Agreement. The Equity Distribution Agreement may be terminated by us in our sole discretion under the circumstances specified in the Equity Distribution Agreement by giving notice to JMP Securities LLC. In addition, JMP Securities LLC may terminate the Equity Distribution Agreement under the circumstances specified in the Equity Distribution Agreement by giving notice to us.

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Potential Conflicts of Interest

JMP Securities LLC and its affiliates have provided, or may in the future provide, various investment banking, commercial banking, financial advisory, brokerage and other services to us and our affiliates for which services they have received, and may in the future receive, customary fees and expense reimbursement. JMP Securities LLC and its affiliates may, from time to time, engage in transactions with and perform services for us in the ordinary course of their business for which they may receive customary fees and reimbursement of expenses. In the ordinary course of their various business activities, JMP Securities LLC and its affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers and such investment and securities activities may involve securities and/or instruments of our company.

The principal business address of JMP Securities LLC is 600 Montgomery Street, San Francisco, CA 94111.

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MANAGEMENT’S DISCUSSION AND ANALYSIS OF

FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The following discussion should be read in conjunction with our consolidated financial statements and related notes and other financial information appearing elsewhere in this prospectus supplement and the accompanying prospectus. In addition to historical information, the following discussion and other parts of this prospectus supplement and the accompanying prospectus contain forward-looking information that involves risks and uncertainties. Our actual results could differ materially from those anticipated by such forward-looking information due to the factors discussed under “Supplementary Risk Factors” and “Forward-Looking Statements” in this prospectus supplement and “Risk Factors” in the accompanying prospectus. Capitalized terms used and not otherwise defined herein have the meaning given in the accompanying prospectus.

Overview

We are a specialty finance company focused on providing senior secured loans to high-growth, innovative venture capital-backed companies in a variety of technology, life sciences, and sustainable and renewable technology industries. We source our investments through our principal office located in Palo Alto, CA, as well as through our additional offices in Boston, MA, New York, NY, Washington, DC, Hartford, CT, and San Diego, CA.

Our goal is to be the leading structured debt financing provider for venture capital-backed companies in technology-related industries requiring sophisticated and customized financing solutions. Our strategy is to evaluate and invest in a broad range of technology-related industries including technology, drug discovery and development, biotechnology, life sciences, healthcare, and sustainable and renewable technology and to offer a full suite of growth capital products. We invest primarily in structured debt with warrants and, to a lesser extent, in senior debt and equity investments. We invest primarily in private companies but also have investments in public companies.

We use the term “structured debt with warrants” to refer to any debt investment, such as a senior or subordinated secured loan, that is coupled with an equity component, including warrants, options or other rights to purchase common or preferred stock. Our structured debt with warrants investments typically are secured by some or all of the assets of the portfolio company. We also provide “unitranche” loans, which are loans that combine both senior and mezzanine debt, generally in a first lien position.

Our investment objective is to maximize our portfolio’s total return by generating current income from our debt investments and capital appreciation from our warrant and equity-related investments. Our primary business objectives are to increase our net income, net operating income and NAV by investing in structured debt with warrants and equity of venture capital-backed companies in technology-related industries with attractive current yields and the potential for equity appreciation and realized gains. Our equity ownership in our portfolio companies may exceed 25% of the voting securities of such companies, which represents a controlling interest under the 1940 Act. In some cases, we receive the right to make additional equity investments in our portfolio companies in connection with future equity financing rounds. Capital that we provide directly to venture capital-backed companies in technology-related industries is generally used for growth and general working capital purposes as well as in select cases for acquisitions or recapitalizations.

We also make investments in qualifying small businesses through our two wholly-owned SBICs. Our SBIC subsidiaries, HT II and HT III, hold approximately $113.1 million and $285.8 million in assets, respectively, and accounted for approximately 5.7% and 14.4% of our total assets, respectively, prior to consolidation at March 31, 2018. In aggregate, at March 31, 2018, with our net investment of $118.5 million, HT II and HT III have the capacity to issue a total of $190.2 million of SBA-guaranteed debentures, subject to SBA approval. At March 31, 2018, we have issued $190.2 million in SBA-guaranteed debentures in our SBIC subsidiaries.

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We have qualified as and have elected to be treated for tax purposes as a RIC under Subchapter M of the Code. Pursuant to this election, we generally will not be subject to corporate-level taxes on any income and gains that we distribute as dividends for federal income tax purposes to our stockholders. However, our qualification and election to be treated as a RIC requires that we comply with provisions contained in Subchapter M of the Code. For example, as a RIC we must earn 90% or more of our gross income during each taxable year from qualified sources, typically referred to as “good income,” as well as satisfy certain quarterly asset diversification and annual income distribution requirements.

We are an internally managed, non-diversified, closed-end investment company that has elected to be regulated as a business development company under the 1940 Act. As a business development company, we are required to comply with certain regulatory requirements. For instance, we generally have to invest at least 70% of our total assets in “qualifying assets,” which includes securities of private U.S. companies, cash, cash equivalents and high-quality debt investments that mature in one year or less.

Our portfolio is comprised of, and we anticipate that our portfolio will continue to be comprised of, investments primarily in technology related companies at various stages of their development. Consistent with requirements under the 1940 Act, we invest primarily in United-States based companies and to a lesser extent in foreign companies.

We regularly engage in discussions with third parties with respect to various potential transactions. We may acquire an investment or a portfolio of investments or an entire company or sell a portion of our portfolio on an opportunistic basis. We, our subsidiaries or our affiliates may also agree to manage certain other funds that invest in debt, equity or provide other financing or services to companies in a variety of industries for which we may earn management or other fees for our services. We may also invest in the equity of these funds, along with other third parties, from which we would seek to earn a return and/or future incentive allocations. Some of these transactions could be material to our business. Consummation of any such transaction will be subject to completion of due diligence, finalization of key business and financial terms (including price) and negotiation of final definitive documentation as well as a number of other factors and conditions including, without limitation, the approval of our board of directors and required regulatory or third party consents and, in certain cases, the approval of our stockholders. Accordingly, there can be no assurance that any such transaction would be consummated. Any of these transactions or funds may require significant management resources either during the transaction phase or on an ongoing basis depending on the terms of the transaction.

Portfolio and Investment Activity

The total fair value of our investment portfolio was approximately $1.5 billion at both March 31, 2018 and December 31, 2017. The fair value of our debt investment portfolio at March 31, 2018 was approximately $1.3 billion, compared to a fair value of approximately $1.4 billion December 31, 2017. The fair value of the equity portfolio at March 31, 2018 was approximately $114.0 million, compared to a fair value of approximately $89.4 million at December 31, 2017. The fair value of the warrant portfolio at March 31, 2018 was approximately $33.3 million, compared to a fair value of approximately $36.8 million at December 31, 2017.

Portfolio Activity

Our investments in portfolio companies take a variety of forms, including unfunded contractual commitments and funded investments. From time to time, unfunded contractual commitments depend upon a portfolio company reaching certain milestones before the debt commitment is available to the portfolio company, which is expected to affect our funding levels. These commitments are subject to the same underwriting and ongoing portfolio maintenance as the on-balance sheet financial instruments that we hold. Debt commitments generally fund over the two succeeding quarters from close. Not all debt commitments represent future cash requirements. Similarly, unfunded contractual commitments may expire without being drawn and thus do not represent future cash requirements.

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Prior to entering into a contractual commitment, we generally issue a non-binding term sheet to a prospective portfolio company. Non-binding term sheets are subject to completion of our due diligence and final investment committee approval process, as well as the negotiation of definitive documentation with the prospective portfolio companies. These non-binding term sheets generally convert to contractual commitments in approximately 90 days from signing. Not all non-binding term sheets are expected to close and do not necessarily represent future cash requirements.

Our portfolio activity for the three months ended March 31, 2018 and the year ended December 31, 2017 was comprised of the following: