The information in this prospectus supplement is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus supplement is not an offer to sell these securities and is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

Filed Pursuant to Rule 497

Registration Statement No.            

PROSPECTUS SUPPLEMENT

(To Prospectus dated            , 201    )

Rights for            Shares

Subscription Rights for Common Stock

Gladstone Investment Corporation, referred to as we, us, our or the Company, is issuing subscription rights, or Rights, to our common stockholders to purchase additional shares of common stock.

We were primarily established for the purpose of investing in subordinated loans, mezzanine debt, preferred stock and warrants to purchase common stock of small and medium-sized companies in connection with buyouts and other recapitalizations. When we invest in buyouts we do so with the management team of the portfolio companies and with other buyout funds. We also sometimes invest in senior secured loans, common stock and, to a much lesser extent, senior and subordinated syndicated loans. Our investment objective is to generate both current income and capital gains through these debt and equity instruments. We operate as a closed-end, non-diversified management investment company and have elected to be treated as a business development company, or BDC, under the Investment Company Act of 1940, as amended, which we refer to as the 1940 Act. Our investment adviser is Gladstone Management Corporation, referred to as Adviser.

Our common stock is traded on The NASDAQ Global Select Market under the symbol “GAIN.” The last reported sale price for our common stock on             ,        was $        per share. The net asset value per share of our common stock at the close of business on            , 201    was $        per share.

You should read this prospectus supplement and the accompanying prospectus before deciding whether to invest in our Rights and you should retain them for future reference. Additional information about us, including our annual, quarterly and current reports, has been filed with the Securities and Exchange Commission. This information is available free of charge on our corporate website at http://www.gladstoneinvestment.com.

Investing in common stock through Rights involves certain risks that are described in the “Risk Factors” section beginning on page R-7 of this prospectus supplement and page 9 of the accompanying prospectus.

Stockholders who do not exercise their rights may, at the completion of the offering, own a smaller proportional interest in the Company than if they exercised their rights. As a result of the offering you may experience dilution or accretion of the aggregate net asset value of your shares of common stock depending upon whether the Company’s net asset value per share of common stock is above or below the subscription price on the expiration date.

The Rights being offered have not been approved or disapproved by the Securities and Exchange Commission or any state securities commission nor has the Securities and Exchange Commission or any state securities commission passed upon the accuracy or adequacy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

The common stock is expected to be ready for delivery in book-entry form through the Depository Trust Company on or about             , 201    . If the offer is extended, the common stock is expected to be ready for delivery in book-entry form through the Depository Trust Company on or about            , 201    .

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            , 201    

We have not authorized any dealer, salesman or other person to give any information or to make any representation other than those contained in this prospectus supplement or the accompanying prospectus. You must not rely upon any information or representation not contained in this prospectus supplement or the accompanying prospectus as if we had authorized it. This prospectus supplement and the accompanying prospectus do not constitute an offer to sell or a solicitation of any offer to buy any security other than the registered securities to which they relate, nor do they constitute an offer to sell or a solicitation of an offer to buy any securities in any jurisdiction to any person to whom it is unlawful to make such an offer or solicitation in such jurisdiction. The information contained in this prospectus supplement and any accompanying prospectus is accurate as of the dates on their respective covers only. Our business, financial condition, results of operations and prospects may have changed since such dates.

TABLE OF CONTENTS

Prospectus Supplement

Prospectus

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

All statements contained in this prospectus supplement or the accompanying prospectus, other than historical facts, may constitute “forward-looking statements.” These statements may relate to, among other things, future events or our future performance or financial condition. In some cases, you can identify forward-looking statements by terminology such as “may,” “might,” “believe,” “will,” “provided,” “anticipate,” “future,” “could,” “growth,” “plan,” “intend,” “expect,” “should,” “would,” “if,” “seek,” “possible,” “potential,” “likely” or the negative of such terms or comparable terminology. These forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause our actual results, levels of activity, performance or achievements to be materially different from any future results, levels of activity, performance or achievements expressed or implied by such forward-looking statements. Such factors include, among others: (1) further adverse changes in the economy and the capital markets; (2) risks associated with negotiation and consummation of pending and future transactions; (3) the loss of one or more of our executive officers, in particular David Gladstone, Terry Lee Brubaker or David Dullum; (4) changes in our business strategy; (5) availability, terms and deployment of capital; (6) changes in our industry, interest rates, exchange rates or the general economy; (7) the degree and nature of our competition; and (8) those factors described in the “Risk Factors” sections of this prospectus supplement and the accompanying prospectus. We caution readers not to place undue reliance on any such forward-looking statements, which speak only as of the date made. We undertake no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, after the date of this prospectus supplement. The forward-looking statements contained in this prospectus supplement or the accompanying prospectus are excluded from the safe harbor protection provided by the Private Securities Litigation Reform Act of 1995 and Section 27A of the Securities Act.

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SUMMARY OF THE TERMS OF THE RIGHTS OFFERING

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DESCRIPTION OF THE RIGHTS OFFERING

[To be provided.]

FEES AND EXPENSES

The following table is intended to assist you in understanding the costs and expenses that an investor in this offering will bear directly or indirectly. We caution you that some of the percentages indicated in the table below are estimates and may vary. Except where the context suggests otherwise, whenever this prospectus contains a reference to fees or expenses paid by “us” or “Gladstone Investment,” or that “we” will pay fees or expenses, stockholders will indirectly bear such fees or expenses as investors in Gladstone Investment. The following annualized percentages were calculated based on actual expenses incurred in the quarter ended [                    ], and average net assets for the quarter ended [                    ]. The table and examples below include all fees and expenses of our consolidated subsidiaries.

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Examples of how the incentive fee would be calculated are as follows:

= 100% × (2.00% – 1.75%)

= 0.25%

= (100% × (“catch-up”: 2.1875% – 1.75%)) + (20%× (2.30% – 2.1875%))

= (100% × 0.4375%) + (20% × 0.1125%)

= 0.4375% + 0.0225%

= 0.46%

= 20% × (6% – 1%)

= 20% × 5%

= 1%

For a more detailed discussion of the calculation of the two-part incentive fee, see “Management—Certain Transactions—Investment Advisory and Management Agreement.”

Example

The following examples demonstrate 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. In calculating the following expense amounts, we have assumed that our annual operating expenses would remain at the levels set forth in the table above. The amounts set forth below do not reflect the impact of any sales load or offering expenses to be borne by Gladstone Investment and its stockholders. In the prospectus supplement relating to an offering of securities pursuant to this prospectus, the examples below will be restated to reflect the impact of the estimated offering expenses borne by Gladstone Investment and its stockholders and, in the event that securities to which this prospectus relates are sold to or through underwriters, the impact of the applicable sales load. The examples below and

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the expenses in the table above should not be considered a representation of our future expenses, and actual expenses may be greater or less than those shown. While the example assumes, as required by the SEC, a 5% annual return, our performance will vary and may result in a return greater or less than 5%.

RISK FACTORS

[To be provided.]

USE OF PROCEEDS

[To be provided.]

CAPITALIZATION

[To be provided.]

PRICE RANGE OF COMMON STOCK AND DISTRIBUTIONS

We currently intend to distribute in the form of cash dividends, a minimum of 90% of our net ordinary income and net short-term capital gains, if any, on a quarterly basis to our stockholders in the form of monthly dividends. We intend to retain long-term capital gains and treat them as deemed distributions for tax purposes. We report the estimated tax characteristics of each distribution when declared while the actual tax characteristics of distributions are reported annually to each stockholder on IRS Form 1099 — DIV. There is no assurance that we will achieve investment results or maintain a tax status that will permit any specified level of cash distributions or year-to-year increases in cash distributions. At the option of a holder of record of common stock, all cash distributions can be reinvested automatically under our dividend reinvestment plan in additional whole and fractional shares. A stockholder whose shares are held in the name of a broker or other nominee should contact the broker or nominee regarding participation in our dividend reinvestment plan on the stockholder’s behalf. See “Risk Factors — We will be subject to corporate-level tax if we are unable to satisfy Code requirements for RIC qualification;” “Dividend Reinvestment Plan;” and “Material U.S. Federal Income Tax Considerations” in the accompanying prospectus.

Our common stock is quoted on The NASDAQ Global Select Market under the symbol “GAIN.” Our common stock has historically traded at prices both above and below its net asset value. There can be no assurance, however, that any premium to net asset value will be attained or maintained. As of             ,         , we had [    ] stockholders of record.

TAXATION

[To be provided.]

LEGAL MATTERS

The legality of securities offered hereby will be passed upon for us by Bass, Berry & Sims PLC, Nashville, Tennessee. [Certain legal matters will be passed upon for the underwriters by                     .]

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Gladstone Investment Corporation

        Shares of Common Stock

Issuable Upon Exercise of Rights to

Subscribe for Such Shares of Common Stock

PROSPECTUS SUPPLEMENT

            , 201    

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