Filed Pursuant to Rule 497
Registration Statement No. 333-223350

This preliminary prospectus supplement relates to an effective registration statement under the Securities Act of 1933, as amended, but the information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell, and are not soliciting an offer to buy, these securities in any jurisdiction where the offer and sale is not permitted.

SUBJECT TO COMPLETION, DATED FEBRUARY 5, 2019

PRELIMINARY PROSPECTUS SUPPLEMENT

(To Prospectus dated May 2, 2018)

$                

        % Notes due 2024

We are an externally managed, closed-end, non-diversified management investment company that has elected to be regulated as a business development company, or BDC, under the Investment Company Act of 1940, as amended, or the 1940 Act. Our investment objective is to provide attractive risk-adjusted returns by generating both current income from our debt investments and capital appreciation from our equity related investments. Our strategy includes partnering with business owners, management teams and financial sponsors by providing customized financing for ownership transactions, recapitalizations, strategic acquisitions, business expansion and other growth initiatives. We generally invest in securities that would be rated below investment grade if they were rated by rating agencies. Below investment grade securities, which are often referred to as “high yield” or “junk,” have speculative characteristics with respect to the issuer’s capacity to pay interest and repay principal.

Fidus Investment Advisors, LLC serves as our investment advisor and as our administrator.

We are offering $            million in aggregate principal amount of     % notes due 2024, which we refer to as the Notes. The Notes will mature on                 , 2024. We will pay interest on the Notes on February 15, May 15, August 15 and November 15 of each year, beginning May 15, 2019. We may redeem the Notes in whole or in part at any time or from time to time on or after                    , 2021, at the redemption price of 100% plus accrued and unpaid interest, as discussed under the section titled “Description of the Notes—Optional Redemption” in this prospectus supplement. The Notes will be issued in minimum denominations of $25 and integral multiples of $25 in excess thereof.

The underwriters may also purchase up to an additional $            million aggregate principal amount of Notes offered by this prospectus supplement and the accompanying prospectus, within 30 days of the date of this prospectus supplement solely to cover over-allotments, if any. If the underwriters exercise this over-allotment option in full, the total aggregate proceeds to us, before deducting expenses payable by us, will be $            .

The Notes will be our direct unsecured obligations and rank pari passu, which means equal in right of payment, with all outstanding and future unsecured unsubordinated indebtedness issued by us, including, without limitation, our 5.875% notes due 2023 (the “2023 Notes”), of which $50.0 million in aggregate principal was outstanding as of February 4, 2019. Because the Notes will not be secured by any of our assets, they will be effectively subordinated to all of our existing and future secured indebtedness (or any indebtedness that is initially unsecured as to which we subsequently grant a security interest), to the extent of the value of the assets securing such indebtedness, including, without limitation, borrowings under our senior secured revolving credit facility with ING Capital LLC, or ING, as amended, or the Credit Facility, of which we had $75.0 million outstanding as of February 4, 2019. The Notes will be structurally subordinated to all existing and future indebtedness and other obligations of any of our existing or future subsidiaries since the Notes are obligations exclusively of Fidus Investment Corporation and not of any of our subsidiaries. As of February 4, 2019, our subsidiaries had total indebtedness outstanding of $191.0 million. None of our subsidiaries is a guarantor of the Notes and the Notes will not be required to be guaranteed by any subsidiary we may acquire or create in the future. For further discussion, see the section titled “Description of the Notes” in this prospectus supplement.

The Notes will also rank pari passu with, or equal to, our general liabilities (total liabilities, less debt). In total, these general liabilities were $17.0 million as of September 30, 2018. We currently do not have outstanding debt that is subordinated to the Notes and do not currently intend to issue indebtedness that expressly provides that it is subordinated to the Notes. Therefore, the Notes will not be senior to any of our indebtedness or obligations.

We intend to list the Notes on The Nasdaq Global Select Market, and we expect trading to commence thereon within 30 days of the original issue date under the trading symbol “FDUSZ”. We have agreed to a covenant relating to the listing of the Notes, which is described under the headings “Specific Terms of the Notes and Offering—Other Covenants” and “Description of the Notes—Covenants” in this prospectus supplement. The Notes are expected to trade “flat.” This means that purchasers will not pay, and sellers will not receive, any accrued and unpaid interest on the Notes that is not included in the trading price. Currently, there is no public market for the Notes, and there can be no assurance that one will develop.

This prospectus supplement and the accompanying prospectus contain important information about us that a prospective investor should know before investing in the Notes. Please read this prospectus supplement and the accompanying prospectus before investing in the Notes and keep them for future reference. We file annual, quarterly and current reports, proxy statements and other information with the Securities and Exchange Commission, or the SEC. This information is also available free of charge by contacting us at 1603 Orrington Avenue, Suite 1005, Evanston, Illinois 60201, Attention: Investor Relations, or by calling us at (847) 859-3940 or on our website at www.fdus.com. Information contained on our website is not incorporated by reference into this prospectus supplement or the accompanying prospectus, and you should not consider that information to be part of this prospectus supplement or the accompanying prospectus. The SEC also maintains a website at www.sec.gov that contains such information.

Investing in the Notes involves a high degree of risk, and should be considered highly speculative. See “Supplementary Risk Factors ” beginning on page S-18 of this prospectus supplement and “Risk Factors” beginning on page 13 of the accompanying prospectus to read about factors you should consider, including the risk of leverage, before investing in the Notes.

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

The underwriters may also purchase up to an additional $            total aggregate principal amount of Notes offered by this prospectus supplement and the accompanying prospectus, solely to cover over-allotments, if any, within 30 days of the date of this prospectus supplement. If the underwriters exercise this option in full, the total public offering price will be $            , the total underwriting discount (sales load and commissions) paid by us will be $            , and total proceeds, before expenses, will be $            .

THE NOTES ARE NOT DEPOSITS OR OTHER OBLIGATIONS OF A BANK AND ARE NOT INSURED BY THE FEDERAL DEPOSIT INSURANCE CORPORATION OR ANY OTHER GOVERNMENT AGENCY.

Delivery of the Notes in book-entry form only through The Depository Trust Company, known as DTC, will be made on or about                 , 2019.

Sole Bookrunner

Keefe, Bruyette & Woods,

                                  A Stifel Company

Co-Leads

BB&T Capital Markets    Janney Montgomery Scott    Ladenburg Thalmann

Co-Managers

B. Riley FBR William Blair

The date of this prospectus supplement is February     , 2019

TABLE OF CONTENTS

Prospectus Supplement

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ABOUT THE PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of the Notes we are offering and certain other matters relating to us. The second part, the accompanying prospectus, gives more general information about the securities that we may offer from time to time, some of which may not apply to the Notes offered by this prospectus supplement.

If information varies between this prospectus supplement and the accompanying prospectus, you should rely only on such information in this prospectus supplement. The information contained in this prospectus supplement supersedes any inconsistent information included in the accompanying prospectus. In various places in this prospectus supplement and the accompanying prospectus, we refer you to other sections of such documents for additional information by indicating the caption heading of such other sections. The page on which each principal caption included in this prospectus supplement and the accompanying prospectus can be found is listed in the table of contents above. All such cross references in this prospectus supplement are to captions contained in this prospectus supplement and not in the accompanying prospectus, unless otherwise stated.

YOU SHOULD RELY ONLY ON THE INFORMATION CONTAINED IN THIS PROSPECTUS SUPPLEMENT AND THE ACCOMPANYING PROSPECTUS. WE HAVE NOT, AND THE UNDERWRITERS HAVE NOT, AUTHORIZED ANY OTHER PERSON TO PROVIDE YOU WITH DIFFERENT OR ADDITIONAL INFORMATION. IF ANYONE PROVIDES YOU WITH DIFFERENT OR ADDITIONAL INFORMATION, YOU SHOULD NOT RELY ON IT. WE ARE NOT, AND THE UNDERWRITERS ARE NOT, MAKING AN OFFER TO SELL THESE NOTES IN ANY JURISDICTION WHERE THE OFFER OR SALE IS NOT PERMITTED. YOU SHOULD ASSUME THAT THE INFORMATION APPEARING IN THIS PROSPECTUS SUPPLEMENT AND THE ACCOMPANYING PROSPECTUS IS ACCURATE ONLY AS OF ITS DATE, REGARDLESS OF THE TIME OF DELIVERY OF THIS PROSPECTUS SUPPLEMENT AND THE ACCOMPANYING PROSPECTUS OR ANY SALES OF THE NOTES. OUR BUSINESS, FINANCIAL CONDITION, RESULTS OF OPERATIONS AND PROSPECTS MAY HAVE CHANGED SINCE THOSE DATES.

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SUPPLEMENTARY RISK FACTORS

Investing in the Notes involves a high degree of risk. Before you invest in the Notes, you should be aware of various significant risks, including those described below. You should carefully consider these risks, together with all of the other information included in this prospectus supplement and the accompanying prospectus, before you decide whether to make an investment in the Notes. The risks set forth below are not the only risks we face. If any of the following risks occur, our business, financial condition and results of our operations could be materially adversely affected. In such case, you could lose all or part of your investment.

Risks Related to the Notes

The Notes will be unsecured and therefore will be effectively subordinated to any secured indebtedness we have currently incurred or may incur in the future and will rank pari passu with, or equal to, all outstanding and future unsecured unsubordinated indebtedness issued by us and our general liabilities.

The Notes will not be secured by any of our assets or any of the assets of any of our subsidiaries. As a result, the Notes will be effectively subordinated to any secured indebtedness we or our subsidiaries have outstanding as of the date of this prospectus supplement (including our Credit Facility) or that we or our subsidiaries may incur in the future (or any indebtedness that is initially unsecured as to which we subsequently grant a security interest) to the extent of the value of the assets securing such indebtedness. In any liquidation, dissolution, bankruptcy or other similar proceeding, the holders of any of our secured indebtedness or secured indebtedness of our subsidiaries may assert rights against the assets pledged to secure that indebtedness in order to receive full payment of their indebtedness before the assets may be used to pay other creditors, including the holders of the Notes. As of February 4, 2019, we had $75.0 million in outstanding indebtedness under our Credit Facility. The indebtedness under the Credit Facility is effectively senior to the Notes to the extent of the value of the assets securing such indebtedness.

The Notes will be structurally subordinated to the indebtedness and other liabilities of our subsidiaries.

The Notes will be obligations exclusively of Fidus Investment Corporation, and not of any of our subsidiaries. None of our subsidiaries will be a guarantor of the Notes, and the Notes will not be required to be guaranteed by any subsidiary we may acquire or create in the future. Any assets of our subsidiaries will not be directly available to satisfy the claims of our creditors, including holders of the Notes. Except to the extent we are a creditor with recognized claims against our subsidiaries, all claims of creditors of our subsidiaries will have priority over our equity interests in such entities (and therefore the claims of our creditors, including holders of the Notes) with respect to the assets of such entities. Even if we are recognized as a creditor of one or more of these entities, our claims would still be effectively subordinated to any security interests in the assets of any such entity and to any indebtedness or other liabilities of any such entity senior to our claims. Consequently, the Notes will be structurally subordinated to all indebtedness and other liabilities, including trade payables, of any of our existing or future subsidiaries, including the Funds. As of February 4, 2019, our subsidiaries had total indebtedness outstanding of $191.0 million. Certain of these entities currently serve as guarantors under our Credit Facility, and in the future our subsidiaries may incur substantial additional indebtedness, all of which is and would be structurally senior to the Notes.

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The indenture under which the Notes will be issued contains limited protection for holders of the Notes.

The indenture under which the Notes will be issued offers limited protection to holders of the Notes. The terms of the indenture and the Notes do not restrict our or any of our subsidiaries’ ability to engage in, or otherwise be a party to, a variety of corporate transactions, circumstances or events that could have a material adverse impact on your investment in the Notes. In particular, the terms of the indenture and the Notes will not place any restrictions on our or our subsidiaries’ ability to:

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In addition, the indenture (as defined in “Description of the Notes”) will not require us to make an offer to purchase the Notes in connection with a change of control or any other event.

Furthermore, the terms of the indenture and the Notes do not protect holders of the Notes in the event that we experience changes (including significant adverse changes) in our financial condition, results of operations or credit ratings, if any, as they do not require that we or our subsidiaries adhere to any financial tests or ratios or specified levels of net worth, revenues, income, cash flow, or liquidity other than as described under “Description of the Notes—Events of Default” and “Description of the Notes—Covenants” elsewhere in this prospectus supplement.

Our ability to recapitalize, incur additional debt (including additional debt that matures prior to the maturity of the Notes), and take a number of other actions that are not limited by the terms of the Notes may have important consequences for you as a holder of the Notes, including making it more difficult for us to satisfy our obligations with respect to the Notes or negatively affecting the trading value of the Notes.

Other debt we issue or incur in the future could contain more protections for its holders than the indenture and the Notes, including additional covenants and events of default. The issuance or incurrence of any such debt with incremental protections could affect the market for, trading levels, and prices of the Notes.

There is no existing trading market for the Notes and, even if The Nasdaq Global Select Market approves the listing of the Notes, an active trading market for the Notes may not develop, which could limit your ability to sell the Notes and/or the market price of the Notes.

The Notes will be a new issue of debt securities for which there initially will not be a trading market. We intend to list the Notes on The Nasdaq Global Select Market within 30 days of the original issue date under the symbol “FDUSZ”. However, there is no assurance that the Notes will be approved for listing on The Nasdaq Global Select Market.

Moreover, even if the listing of the Notes is approved, we cannot provide any assurances that an active trading market will develop or be maintained for the Notes or that you will be able to sell

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your Notes. If the Notes are traded after their initial issuance, they may trade at a discount from their initial offering price depending on prevailing interest rates, the market for similar securities, our credit ratings, if any, general economic conditions, our financial condition, performance and prospects and other factors. The underwriters have advised us that they intend to make a market in the Notes, but they are not obligated to do so. The underwriters may discontinue any market-making in the Notes at any time at their sole discretion.

Accordingly, we cannot assure you that the Notes will be approved for listing on The Nasdaq Global Select Market, that a liquid trading market will develop or be maintained for the Notes, that you will be able to sell your Notes at a particular time or that the price you receive when you sell will be favorable. To the extent an active trading market does not develop, the liquidity and trading price for the Notes may be harmed. Accordingly, you may be required to bear the financial risk of an investment in the Notes for an indefinite period of time.

Our amount of debt outstanding will increase as a result of this offering, and if we default on our obligations to pay our other indebtedness, we may not be able to make payments on the Notes.

As of February 4, 2019, we had approximately $75.0 million of indebtedness outstanding under the Credit Facility and $50.0 million in aggregate principal of our 2023 Notes outstanding. Any default under the agreements governing our indebtedness, including a default under our Credit Facility, the indenture governing our 2023 Notes or other indebtedness to which we may be a party that is not waived by the required lenders or holders, and the remedies sought by lenders or the holders of such indebtedness could make us unable to pay principal, premium, if any, and interest on the Notes and substantially decrease the market value of the Notes. If we are unable to generate sufficient cash flow and are otherwise unable to obtain funds necessary to meet required payments of principal, premium, if any, and interest on our indebtedness, or if we otherwise fail to comply with the various covenants, including financial and operating covenants, as applicable, in the instruments governing our indebtedness (including the Credit Facility, the Notes, and the 2023 Notes), we could be in default under the terms of the agreements governing such indebtedness. In the event of such default, the holders of such indebtedness could elect to declare all the funds borrowed thereunder to be due and payable, together with accrued and unpaid interest; the lenders under the Credit Facility or other revolving credit facility we may incur in the future could elect to terminate their commitment, cease making further loans and institute foreclosure proceedings against our assets; and we could be forced into bankruptcy or liquidation.

Our ability to generate sufficient cash flow in the future is, to some extent, subject to general economic, financial, competitive, legislative and regulatory factors as well as other factors that are beyond our control. We cannot assure you that our business will generate cash flow from operations, or that future borrowings will be available to us under the Credit Facility or otherwise, in an amount sufficient to enable us to meet our payment obligations under the Notes, our other debt, and to fund other liquidity needs.

In this regard, our Credit Facility is scheduled to mature on June 16, 2019. We are in the process of negotiating a renewal and extension of our Credit Facility, but we cannot assure you that those efforts will be successful. If we fail to negotiate such an extension, and the Credit Facility were to mature on June 16, 2019, as scheduled, then the commitments under the Credit Facility would expire, we would have to repay any then-outstanding borrowings under the Credit Facility, and we would be unable to borrow additional amounts under the Credit Facility, all of which could have a material adverse effect on our ability to make required payments under the Notes and the 2023 Notes, our ability to fund new investments, and our liquidity generally.

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In addition, if our operating performance declines and we are not able to generate sufficient cash flow to service our debt obligations, we may in the future need to refinance or restructure our debt, including any Notes sold, sell assets, reduce or delay capital investments, seek to raise additional capital or seek to obtain waivers from the lenders under the Credit Facility, the holders of our 2023 Notes or other debt that we may incur in the future to avoid being in default. If we are unable to implement one or more of these alternatives, we may not be able to meet our payment obligations under the Notes and our other debt. If we breach our covenants under the Credit Facility, the 2023 Notes or any of our other debt and seek a waiver, we may not be able to obtain a waiver from the required lenders or holders thereof. If this occurs, we would be in default under the Credit Facility, the 2023 Notes or other debt, the lenders or holders could exercise rights as described above, and we could be forced into bankruptcy or liquidation. If we are unable to repay debt, lenders having secured obligations could proceed against the collateral securing the debt, including the Credit Facility. Because the Credit Facility has, and any future credit facilities will likely have, customary cross-default provisions, if we have a default under the terms of the Notes, the obligations under the Credit Facility or any future credit facility may be accelerated and we may be unable to repay or finance the amounts due.

A downgrade, suspension or withdrawal of the credit rating assigned by a rating agency to us or the Notes, if any, or change in the debt markets could cause the liquidity or market value of the Notes to decline significantly.

Our credit ratings are an assessment by rating agencies of our ability to pay our debts when due. Consequently, real or anticipated changes in our credit ratings will generally affect the market value of the Notes. These credit ratings may not reflect the potential impact of risks relating to the structure or marketing of the Notes. Credit ratings are not a recommendation to buy, sell or hold any security, and may be revised or withdrawn at any time by the issuing organization in its sole discretion. Neither we nor any underwriter undertakes any obligation to maintain our credit ratings or to advise holders of Notes of any changes in our credit ratings. There can be no assurance that our credit ratings will remain for any given period of time or that such credit ratings will not be lowered or withdrawn entirely by the rating agencies if in their judgment future circumstances relating to the basis of the credit ratings, such as adverse changes in our company, so warrant. The conditions of the financial markets and prevailing interest rates have fluctuated in the past and are likely to fluctuate in the future, which could have an adverse effect on the market prices of the Notes.

We may choose to redeem the Notes when prevailing interest rates are relatively low.

On or after                     , 2021, we may choose to redeem the Notes from time to time, especially if prevailing interest rates are lower than the rate borne by the Notes. Before redeeming any Notes, we would have to comply with certain requirements under our Credit Facility, to the extent such requirements remain in effect at such time, or otherwise obtain consent from the lenders. If prevailing rates are lower at the time of redemption, and we redeem the Notes, you likely would not be able to reinvest the redemption proceeds in a comparable security at an effective interest rate as high as the interest rate on the Notes being redeemed. Our redemption right also may adversely impact your ability to sell the Notes as the optional redemption date or period approaches.

Legislation that took effect in 2018 would allow us to incur additional leverage.

As a BDC, 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 200.0% (i.e., the amount of debt may not exceed 50.0% of the value of our assets). However,

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legislation that took effect in 2018 has modified the 1940 Act by allowing a BDC to increase the maximum amount of leverage it may incur from an asset coverage ratio of 200.0% to an asset coverage ratio of 150.0%, if certain requirements are met. Under the legislation, we are allowed to increase our leverage capacity if stockholders representing at least a majority of the votes cast, when quorum is met, approve a proposal to do so. If we receive stockholder approval, we would be allowed to increase our leverage capacity on the first day after such approval. Alternatively, the legislation allows the “required majority” of our independent directors, as defined in Section 57(o) of the 1940 Act, to approve an increase in our leverage capacity, and such approval would become effective after one year. In either case, we would be required to make certain disclosures on our website and in SEC filings regarding, among other things, the receipt of approval to increase our leverage, our leverage capacity and usage, and risks related to leverage.

Leverage magnifies the potential for loss on investments and on invested equity capital. As we use leverage to partially finance our investments, you will experience increased risks of investing in our securities. For example, as we increase our leverage and, as a result, our total interest expense and other required payments on such indebtedness, any decrease in our income would cause net investment income to decline more sharply than it would have had we not borrowed, and the decline could negatively affect our ability to make the required payments on such indebtedness or on our other securities. Increased leverage may also cause a downgrade of our credit rating. Leverage is generally considered a speculative investment technique.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement and the accompanying prospectus contain forward-looking statements that involve substantial risks and uncertainties. These forward-looking statements are not historical facts, but rather are based on current expectations, estimates and projections about us, our current and prospective portfolio investments, our industry, our beliefs, and our assumptions. Words such as “anticipates,” “expects,” “intends,” “plans,” “will,” “may,” “continue,” “believes,” “seeks,” “estimates,” “would,” “should,” “targets,” “projects” and variations of these words and similar expressions are intended to identify forward-looking statements. The forward-looking statements contained in this prospectus supplement and the accompanying prospectus involve risks and uncertainties, including statements as to:

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These statements are not guarantees of future performance and are subject to risks, uncertainties and other factors, some of which are beyond our control and difficult to predict and could cause actual results to differ materially from those expressed or forecasted in the forward-looking statements, including without limitation:

Although we believe that the assumptions on which these forward-looking statements are based are reasonable, any of those assumptions could prove to be inaccurate, and as a result, the forward-looking statements based on those assumptions also could be inaccurate. Important assumptions include our ability to originate new loans and investments, certain margins and levels of profitability and the availability of additional capital. In light of these and other uncertainties, the inclusion of a projection or forward-looking statement in this prospectus should not be regarded as a representation by us that our plans and objectives will be achieved. These risks and uncertainties include those described or identified in “Risk Factors” and elsewhere in this prospectus supplement and the accompanying prospectus. You should not place undue reliance on these forward-looking statements, which apply only as of the date of this prospectus. The forward-looking statements and projections contained in this prospectus supplement and accompanying prospectus are excluded from the safe harbor protection provided by Section 27A of the Securities Act of 1933, as amended, or the Securities Act.

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USE OF PROCEEDS

We estimate that the net proceeds we will receive from the sale of the Notes will be approximately $            million (or approximately $            million if the underwriters exercise their over-allotment option in full) based on a public offering price of $            per Note, after deducting the underwriting discount of $            (or approximately $            if the underwriters fully exercise their over-allotment option) payable by us and estimated offering expenses of approximately $400,000 payable by us. We may change the size of this offering based on demand and market conditions.

We intend to use the net proceeds from this offering to repay outstanding indebtedness under our Credit Facility. However, we may re-borrow under our Credit Facility and use such borrowings to invest in lower middle-market companies in accordance with our investment objective and strategies and for working capital and general corporate purposes. As of February 4, 2019, we had $75.0 million of indebtedness outstanding under our Credit Facility, which is subject to customary covenants and obligations. After giving effect to this offering and the use of the net proceeds therefrom to repay outstanding indebtedness under the Credit Facility (and assuming no exercise of the over-allotment option), we will have under our Credit Facility $            of indebtedness outstanding and $            available to be drawn. Our Credit Facility matures on June 16, 2019, and borrowings under the Credit Facility currently bear interest on a per annum basis equal to (i) the alternate base rate plus 2.5% or (ii) the applicable LIBOR, which varies depending on the period of the borrowing under the Credit Facility, plus 3.5%. The alternate base rate is equal to the greater of (i) prime rate, (ii) the federal funds rate plus 0.5% or (iii) the three-month LIBOR plus 1.0%. See “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Liquidity and Capital Resources” for additional information.

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CAPITALIZATION

The following table sets forth our capitalization as of September 30, 2018:

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

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SELECTED CONSOLIDATED FINANCIAL DATA

The following selected consolidated financial data of Fidus Investment Corporation and its subsidiaries, including the Funds, as of and for the years ended December 31, 2017, 2016, 2015, 2014 and 2013, is derived from the consolidated financial statements that have been audited by RSM US LLP, our independent registered public accounting firm. The selected consolidated financial and other data for the nine months ended September 30, 2018 and other quarterly financial information is derived from our unaudited financial statements, and 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 nine months ended September 30, 2018 are not necessarily indicative of the results that may be expected for the year ended December 31, 2018. This financial data should be read in conjunction with our consolidated financial statements and the notes thereto and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” included in this prospectus supplement and the accompanying prospectus.

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SELECTED QUARTERLY FINANCIAL DATA

The following tables set forth certain quarterly financial information for each of the 11 quarters ending with the quarter ended September 30, 2018 (dollars in thousands, except per share numbers). This information was derived from our unaudited consolidated financial statements. Results for any quarter are not necessarily indicative of results for the past fiscal year or for any future quarter.

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MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with “Selected Consolidated Financial Data,” Fidus Investment Corporation’s consolidated financial statements and related notes appearing elsewhere in this prospectus supplement and the accompanying prospectus. The information contained in this section contains forward-looking statements that involve risks and uncertainties. Please see “Supplemental Risk Factors,” “Risk Factors” and “Special Note Regarding Forward-Looking Statements” in this prospectus supplement and the accompanying prospectus for a discussion of the uncertainties, risks and assumptions associated with these statements.

Overview

General and Corporate Structure

We provide customized debt and equity financing solutions to lower middle-market companies, which we define as U.S. based companies having revenues between $10.0 million and $150.0 million. Our investment objective is to provide attractive risk-adjusted returns by generating both current income from our debt investments and capital appreciation from our equity related investments. Our investment strategy includes partnering with business owners, management teams and financial sponsors by providing customized financing for ownership transactions, recapitalizations, strategic acquisitions, business expansion and other growth initiatives. We seek to maintain a diversified portfolio of investments in order to help mitigate the potential effects of adverse economic events related to particular companies, regions or industries.

FIC was formed as a Maryland corporation on February 14, 2011. We completed our initial public offering, or IPO, in June 2011.

On June 20, 2011, FIC acquired all of the limited partnership interests of Fund I and membership interests of Fidus Mezzanine Capital GP, LLC, its general partner, resulting in Fund I becoming our wholly-owned SBIC subsidiary. Immediately following the acquisition, we and Fund I elected to be treated as business development companies, or BDCs, under the 1940 Act and our investment activities have been managed by Fidus Investment Advisors, LLC, our investment advisor, and supervised by our board of directors, a majority of whom are independent of us. On March 29, 2013, we commenced operations of a second wholly-owned subsidiary, Fund II. Fund I and Fund II are collectively referred to as the “Funds.”

Fund I received its SBIC license on October 22, 2007 and Fund II received its SBIC license on May 28, 2013. We plan to continue to operate the Funds as SBICs, subject to SBA approval, and to utilize the proceeds of the sale of SBA-guaranteed debentures to enhance returns to our stockholders. We have also made, and continue to make, investments directly through FIC. We believe that utilizing FIC and the Funds as investment vehicles provides us with access to a broader array of investment opportunities. Based on the current capitalization of the Funds, we have fully utilized our borrowing capacity under the SBIC debenture program.

We have certain wholly-owned taxable subsidiaries (the “Taxable Subsidiaries”), each of which generally holds one or more of our portfolio investments listed on the consolidated schedules of investments. The Taxable Subsidiaries are consolidated for financial reporting purposes, such that the our consolidated financial statements reflect our investment in the portfolio company investments owned by the Taxable Subsidiaries. The purpose of the Taxable Subsidiaries is to permit us to hold equity investments in portfolio companies that are taxed as

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partnerships for U.S. federal income tax purposes (such as entities organized as limited liability companies (“LLCs”) or other forms of pass through entities) while complying with the “source-of-income” requirements contained in the RIC tax provisions. The Taxable Subsidiaries are not consolidated with us for U.S. federal corporate income tax purposes, and each Taxable Subsidiary will be subject to U.S. federal corporate income tax on its taxable income. Any such income or expense is reflected in the consolidated statements of operations.

Investments

We seek to create a diversified investment portfolio that primarily includes loans and, to a lesser extent, equity securities. Our investments typically range between $5.0 million to $30.0 million per portfolio company, although this investment size may vary proportionately with the size of our capital base. Our investment objective is to provide attractive risk-adjusted returns by generating both current income from our debt investments and capital appreciation from our equity related investments. We may invest in the equity securities of our portfolio companies, such as preferred stock, common stock, warrants and other equity interests, either directly or in conjunction with our debt investments.

Second Lien Debt. The majority of our debt investments take the form of second lien debt, which includes senior subordinated notes. Second lien debt investments obtain security interests in the assets of the portfolio company as collateral in support of the repayment of such loans. Second lien debt typically is senior on a lien basis to other liabilities in the issuer’s capital structure and has the benefit of a security interest over assets of the issuer, though ranking junior to first lien debt secured by those assets. First lien lenders and second lien lenders typically have separate liens on the collateral, and an intercreditor agreement provides the first lien lenders with priority over the second lien lenders’ liens on the collateral. These loans typically provide for no contractual loan amortization, with all amortization deferred until loan maturity, and may include payment-in-kind (“PIK”) interest, which increases the principal balance over the term and, coupled with the deferred principal payment provision, increases credit risk exposure over the life of the loan.

Subordinated (“Mezzanine”) Debt. These investments are typically structured as unsecured, subordinated notes. Structurally, mezzanine debt usually ranks subordinate in priority of payment to first lien and second lien debt and may not have the benefit of financial covenants common in first lien and second lien debt. Unsecured debt may rank junior as it relates to proceeds in certain liquidations where it does not have the benefit of a lien in specific collateral held by creditors (typically first lien and/or second lien) who have a perfected security interest in such collateral. However, both mezzanine and unsecured debt ranks senior to common and preferred equity in an issuer’s capital structure. These loans typically have relatively higher fixed interest rates (often representing a combination of cash pay and PIK interest) and amortization of principal deferred to maturity. The PIK feature (meaning a feature allowing for the payment of interest in the form of additional principal amount of the loan instead of in cash), which effectively operates as negative amortization of loan principal, coupled with the deferred principal payment provision, increases credit risk exposure over the life of the loan.

First Lien Debt. To a lesser extent, we also structure some of our debt investments as senior secured or first lien debt investments. First lien debt investments are secured by a first priority lien on existing and future assets of the borrower and may take the form of term loans or revolving lines of credit. First lien debt is typically senior on a lien basis to other liabilities in the issuer’s capital structure and has the benefit of a first-priority security interest in assets of the issuer. The security interest ranks above the security interest of any second lien lenders in those assets. Our first lien debt may include stand-alone first lien loans, “last out” first lien loans, or “unitranche”

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loans. Stand-alone first lien loans are traditional first lien loans. All lenders in the facility have equal rights to the collateral that is subject to the first-priority security interest. “Last out” first lien loans have a secondary priority behind super-senior “first out” first lien loans in the collateral securing the loans in certain circumstances. The arrangements for a “last out” first lien loan are set forth in an “agreement among lenders,” which provides lenders with “first out” and “last out” payment streams based on a single lien on the collateral. Since the “first out” lenders generally have priority over the “last out” lenders for receiving payment under certain specified events of default, or upon the occurrence of other triggering events under intercreditor agreements or agreements among lenders, the “last out” lenders bear a greater risk and, in exchange, receive a higher effective interest rate, through arrangements among the lenders, than the “first out” lenders or lenders in stand-alone first lien loans. Agreements among lenders also typically provide greater voting rights to the “last out” lenders than the intercreditor agreements to which second lien lenders often are subject.

Many of our debt investments also include excess cash flow sweep features, whereby principal repayment may be required before maturity if the portfolio company achieves certain defined operating targets. Additionally, our debt investments typically have principal prepayment penalties in the early years of the loan. The majority of our debt investments provide for a fixed interest rate.

Equity Securities. Our equity securities typically consist of either a direct minority equity investment in common or preferred stock or membership/partnership interests of a portfolio company, or we may receive warrants to buy a minority equity interest in a portfolio company in connection with a debt investment. Warrants we receive with our debt investments typically require only a nominal cost to exercise, and thus, as a portfolio company appreciates in value, we may achieve additional investment return from this equity interest. Our equity investments are typically not control-oriented investments, and in many cases, we acquire equity securities as part of a group of private equity investors in which we are not the lead investor. We may structure such equity investments to include provisions protecting our rights as a minority-interest holder, as well as a “put,” or right to sell such securities back to the issuer, upon the occurrence of specified events. In many cases, we may also seek to obtain registration rights in connection with these equity interests, which may include demand and “piggyback” registration rights. Our equity investments typically are made in connection with debt investments to the same portfolio companies.

Revenues: We generate revenue in the form of interest and fee income on debt investments and capital gains and distributions, if any, on equity investments. Our debt investments, whether in the form of mezzanine, senior secured or unitranche loans, typically have terms of five to seven years and bear interest at a fixed rate but may bear interest at a floating rate. In some instances, we receive payments on our debt investments based on scheduled amortization of the outstanding balances. In addition, we receive repayments of some of our debt investments prior to their scheduled maturity dates, which may include prepayment penalties. The frequency or volume of these repayments fluctuates significantly from period to period. Our portfolio activity may reflect the proceeds of sales of securities. In some cases, our investments provide for deferred interest payments or PIK interest. The principal amount of loans and any accrued but unpaid interest generally become due at the maturity date. In addition, we may generate revenue in the form of commitment, origination, amendment, or structuring fees and fees for providing managerial assistance. Debt investment origination fees, OID and market discount or premium, if any, are capitalized, and we accrete or amortize such amounts into interest income. We record prepayment premiums on loans as fee income. Interest and dividend income is recorded on the accrual basis to the extent that we expect to collect such amounts. Debt investments or preferred equity securities are placed on non-accrual status when principal, interest or dividend payments become materially

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past due, or when there is reasonable doubt that principal, interest or dividends will be collected. See “Critical Accounting Policies and Use of Estimates—Revenue Recognition.” Interest is accrued daily based on the outstanding principal amount and the contractual terms of the debt. Dividend income is recorded as dividends are declared or at the point an obligation exists for the portfolio company to make a distribution, and is generally recognized when received. Distributions of earnings from portfolio companies are evaluated to determine if the distribution is a distribution of earnings or a return of capital. Distributions of earnings are included in dividend income while a return of capital is recorded as a reduction in the cost basis of the investment. Estimates are adjusted as necessary after the relevant tax forms are received from the portfolio company.

We recognize realized gains or losses on investments based on the difference between the net proceeds from the disposition and the cost basis of the investment, without regard to unrealized gains or losses previously recognized. We record current period changes in fair value of investments that are measured at fair value as a component of the net change in unrealized appreciation (depreciation) on investments in the consolidated statements of operations.

Expenses: All investment professionals of our investment advisor and/or its affiliates, when and to the extent engaged in providing investment advisory and management services to us, and the compensation and routine overhead expenses allocable to personnel who provide these services to us, are provided and paid for by our investment advisor and not by us. We bear all other out-of-pocket costs and expenses of our operations and transactions, including, without limitation, those relating to:

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Portfolio Composition, Investment Activity and Yield

During the nine months ended September 30, 2018 and 2017, we invested $144.6 million and $155.6 million in debt and equity investments, respectively, including 12 and 10 new portfolio companies, respectively. During the nine months ended September 30, 2018 and 2017, we received proceeds from sales or repayments, including principal, return of capital dividends and net realized gains (losses), of $92.1 million and $132.7 million, respectively, including exits of nine and four portfolio companies, respectively. The following table summarizes investment purchases and sales and repayments of investments by type for the nine months ended September 30, 2018 and 2017 (dollars in millions).

As of September 30, 2018, the fair value of our investment portfolio totaled $668.5 million and consisted of 65 active portfolio companies and one portfolio company that has sold its underlying operations. As of September 30, 2018, five debt investments bore interest at a variable rate, which represented $44.8 million of our portfolio on a fair value basis, and the remainder of our debt portfolio was comprised of fixed rate investments. Overall, the portfolio had net unrealized appreciation of $48.7 million as of September 30, 2018. As of September 30, 2018, our average active portfolio company investment at amortized cost was $9.5 million, which excludes investments in the one portfolio company that has sold its underlying operations.

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As of December 31, 2017, the fair value of our investment portfolio totaled $596.3 million and consisted of 60 active portfolio companies and three portfolio companies that have sold their underlying operations. As of December 31, 2017, three debt investments bore interest at a variable rate, which represented $26.1 million of our portfolio on a fair value basis, and the remainder of our debt portfolio was comprised of fixed rate investments. Overall, the portfolio had net unrealized appreciation of $18.5 million as of December 31, 2017. As of December 31, 2017, our average active portfolio company investment at amortized cost was $9.6 million, which excludes investments in the three portfolio companies that have sold their underlying operations.

The weighted average yield on debt investments as of September 30, 2018 and December 31, 2017 was 12.6% and 13.0%, respectively. The weighted average yield of our debt investments is not the same as a return on investment for our stockholders but, rather, relates to a portion of our investment portfolio and is calculated before the payment of all of our and our subsidiaries’ fees and expenses. The weighted average yields were computed using the effective interest rates for debt investments at cost as of September 30, 2018 and December 31, 2017, respectively, including the accretion of OID and loan origination fees, but excluding investments on non-accrual status, if any.

The following table shows the portfolio composition by investment type at fair value and cost and as a percentage of total investments (dollars in millions):

The following table shows portfolio composition by geographic region at fair value and cost and as a percentage of total investments (dollars in millions). The geographic composition is determined by the location of the corporate headquarters of the portfolio company, which may not be indicative of the primary source of the portfolio company’s business.

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The following table shows the detailed industry composition of our portfolio at fair value and cost as a percentage of total investments:

Portfolio Asset Quality

In addition to various risk management and monitoring tools, our investment advisor uses an internally developed investment rating system to characterize and monitor the credit profile and our expected level of returns on each investment in our portfolio. We use a five-level numeric rating scale. The following is a description of the conditions associated with each investment rating:

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The following table shows the distribution of our investments on the 1 to 5 investment rating scale at fair value and cost as of September 30, 2018 and December 31, 2017 (dollars in millions):

Based on our investment rating system, the weighted average rating of our portfolio as of September 30, 2018 and December 31, 2017 was 1.9 and 1.9, respectively, on a fair value basis and 2.1 and 2.1, respectively, on a cost basis.

Non-Accrual

As of September 30, 2018 and December 31, 2017, we had debt investments in two portfolio companies on non-accrual status, respectively (dollars in millions):