QuickLinks -- Click here to rapidly navigate through this document

As filed with the Securities and Exchange Commission on May 17, 2010

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

1933 Act File No. 333-162592

Form N-2

REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

GLADSTONE CAPITAL CORPORATION
(Exact name of registrant as specified in charter)

1521 WESTBRANCH DRIVE, SUITE 200
MCLEAN, VA 22102
(Address of principal executive offices)

Registrant's telephone number, including area code: (703) 287-5800

DAVID GLADSTONE
CHAIRMAN AND CHIEF EXECUTIVE OFFICER
GLADSTONE CAPITAL CORPORATION
1521 WESTBRANCH DRIVE, SUITE 200
MCLEAN, VIRGINIA 22102
(Name and address of agent for service)

COPIES TO:

THOMAS R. SALLEY, ESQ.
DARREN K. DESTEFANO, ESQ.
CHRISTINA L. NOVAK, ESQ.
COOLEY GODWARD KRONISH LLP
ONE FREEDOM SQUARE
RESTON TOWN CENTER
11951 FREEDOM DRIVE
RESTON, VIRGINIA 20190
(703) 456-8000
(703) 456-8100 (facsimile)

Approximate date of proposed public offering:
From time to time after the effective date of this registration statement.

---

         If any securities being registered on this form will be offered on a delayed or continuous basis in reliance on Rule 415 under the Securities Act of 1933, as amended, other than securities offered in connection with a dividend reinvestment plan, check the following box. ý

---

EXPLANATORY NOTE

        This Post-Effective Amendment No. 1 to the Registration Statement on From N-2 (File No. 333-162592) of Gladstone Capital Corporation (the "Registration Statement") is being filed pursuant to Rule 462(d) under the Securities Act of 1933, as amended (the "Securities Act"), solely for the purpose of filing exhibits to the Registration Statement. Accordingly, this Post-Effective Amendment No. 1 consists only of a facing page, this explanatory note and Part C of the Registration Statement on Form N-2 setting forth the exhibits to the Registration Statement. This Post-Effective Amendment No. 1 does not modify any other part of the Registration Statement. Pursuant to Rule 462(d) under the Securities Act, this Post-Effective Amendment No. 1 shall become effective immediately upon filing with the Securities and Exchange Commission. The contents of the Registration Statement are hereby incorporated by reference.

---

Part C—OTHER INFORMATION

Item 25.    Financial Statements and Exhibits

1.

Financial Statements

        The following financial statements of Gladstone Capital Corporation (the "Company" or the "Registrant") are included in the Registration Statement in "Part A: Information Required in a Prospectus:"

GLADSTONE CAPITAL CORPORATION
INDEX TO CONSOLIDATED FINANCIAL STATEMENTS

C-1

---

2.

Exhibits

C-2

---

Item 26.    Marketing Arrangements

        The information contained under the heading "Plan of Distribution" on page 119 of the prospectus is incorporated herein by reference, and any information concerning any underwriters will be contained in the accompanying prospectus supplement, if any.

C-3

---

Item 27.    Other Expenses of Issuance and Distribution

        All of the expenses set forth above shall be borne by the Registrant.

Item 28.    Persons Controlled by or Under Common Control

        Gladstone Business Loan, LLC, a Delaware limited liability company and wholly-owned subsidiary of the Registrant.

        Gladstone Financial Corporation, a Delaware corporation and wholly-owned subsidiary of the Registrant.

        BERTL, Inc., a Delaware corporation and wholly-owned subsidiary of the Registrant.

        LYP Holdings Corp., a Delaware corporation controlled by the Registrant.

        LocalTel, LLC, a Delaware limited liability company controlled by LYP Holdings Corp., through 40% ownership.

        LYP, LLC, a Delaware limited liability company controlled by LYP Holdings Corp., through 100% ownership.

        Lindmark Acquisition, LLC a Delaware limited liability company controlled by Lindmark Holdings Corp., through 50% ownership.

        Lindmark Holdings Corp., a Delaware corporation controlled by the Registrant.

        Gladstone SBIC GP, LLC, a Delaware limited liability company and wholly-owned subsidiary of the Registrant.

        Gladstone SBIC, LP, a Delaware limited partnership controlled by Gladstone SBIC GP, LLC, its general partner.

        Defiance Integrated Technologies, Inc., a Delaware corporation controlled by the Registrant through 58% ownership.

        1090 Perry Acquisition Corp., a Delaware corporation controlled by Defiance Integrated Technologies, Inc., through 100% ownership.

        JBM Tool & Die, Inc., a Delaware corporation controlled by Defiance Integrated Technologies, Inc., through 100% ownership.

        Pro Shear Corporation, a Delaware corporation controlled by Defiance Integrated Technologies, Inc., through 100% ownership.

        Gladstone Capital Advisers, Inc., a Delaware corporation and wholly-owned subsidiary of the Registrant.

        U.S. Healthcare Communications, Inc., a Delaware corporation and wholly-owned subsidiary of the Registrant.

        USHC Legal Inc., a New Jersey corporation and wholly-owned subsidiary of the Registrant.

        Directories Holdings, Inc., a Delaware corporation and wholly-owned subsidiary of the Registrant.

C-4

---

        Western Directories, Inc., a Delaware corporation controlled by Directories Holdings, Inc. through 51% ownership.

        Northern Virginia SBIC GP, LLC, a Delaware limited liability company and wholly-owned subsidiary of the Registrant.

        Northern Virginia SBIC, L.P., a Delaware partnership controlled by Northern Virginia SBIC GP, LLC, its general partner.

        Gladstone Investment Corporation, a Delaware corporation controlled by the Registrant's officers and directors.

        Gladstone Investment Advisers, Inc., a Delaware corporation and wholly-owned subsidiary of Gladstone Investment Corporation.

        Cavert II Holding Corp., a Delaware corporation and wholly owned subsidiary of Gladstone Investment Corporation.

        Cavert Wire Holding, Inc., a Delaware corporation, controlled by Cavert II Holding Corp. through 63% ownership of issued and outstanding voting securities.

        A. Stucki Holding Corp., a Delaware corporation, controlled by Gladstone Investment Corporation through 55% ownership.

        ACME Cryogenics Inc., a Pennsylvania corporation controlled by Gladstone Investment Corporation through 82% ownership.

        CCE Investment Corp., a Delaware corporation and wholly-owned subsidiary of Gladstone Investment Corporation.

        Country Club Enterprises, LLC, a Massachusetts limited liability company, controlled by CCE Investment Corp. through 48% ownership.

        Chase II Holding Corp., a Delaware corporation controlled by Gladstone Investment Corporation through 55% ownership of issued and outstanding voting securities.

        ASH Holdings Corp., a Delaware corporation and wholly-owned subsidiary of Gladstone Investment Corporation.

        Auto Safety House, LLC, a Delaware limited liability company, controlled by ASH Holdings, Corp. through 74% ownership.

        Quench Holdings Corp., a Delaware corporation and wholly-owned subsidiary of Gladstone Investment Corporation.

        Galaxy Tool Holding Corporation, a Delaware corporation controlled by Gladstone Investment Corporation through 40% ownership.

        Mathey Investments, Inc., a Oklahoma corporation controlled by Gladstone Investment Corporation.

        Gladstone Business Investment, LLC, a Delaware limited liability company and wholly-owned subsidiary of Gladstone Investment Corporation.

        Gladstone Commercial Corporation, a Maryland corporation controlled by the Registrant's officers and directors.

        GCLP Business Trust I, a Massachusetts business trust controlled by Gladstone Commercial Corporation.

        Gladstone Commercial Partners, LLC, a Delaware limited liability company and wholly-owned subsidiary of Gladstone Commercial Corporation.

C-5

---

        GCLP Business Trust II, a Massachusetts business trust controlled by Gladstone Commercial Partners, LLC.

        Gladstone Commercial Advisers, Inc., a Delaware corporation and wholly-owned subsidiary of Gladstone Commercial Corporation.

        First Park Ten COCO San Antonio GP LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        First Park Ten COCO San Antonio LP, a Delaware limited partnership controlled by its general partner, First Park Ten COCO San Antonio GP LLC.

        COCO04 Austin TX GP LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        COCO04 Austin TX LP, a Delaware limited partnership controlled by its general partner, COCO04 Austin TX GP LLC.

        Pocono PA GCC, LP, a Delaware limited partnership controlled by its general partner, Pocono PA GCC GP LLC.

        Gladstone Commercial Limited Partnership, a Delaware limited partnership controlled by its general partner GCLP Business Trust II.

        GCC Acquisition Holdings LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        SLEE Grand Prairie LP, a Delaware limited partnership controlled by its general partner, GCC Acquisition Holdings, Inc.

        EE 208 South Rogers Lane, Raleigh, NC LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        Gladstone Commercial Lending LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        260 Springside Drive Akron OH LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        Little Arch04 Charlotte NC Member LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        Little Arch Charlotte NC LLC, a Delaware limited liability company controlled by its sole member, Little Arch04 Charlotte NC Member LLC.

        CMI04 Canton NC LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        OB Midway NC Gladstone Commercial LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        GCC Granby LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        Granby Property Trust, a Delaware statutory trust controlled by its grantor, GCC Granby LLC.

        GCC Dorval LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        Dorval Property Trust, a Delaware statutory trust controlled by its grantor, GCC Dorval LLC.

        3094174 Nova Scotia Company, a Nova Scotia corporation controlled by its sole stockholder, Gladstone Commercial Limited Partnership.

C-6

---

        3094175 Nova Scotia Company, a Nova Scotia corporation controlled by its sole stockholder, Gladstone Commercial Limited Partnership.

        GCC Norfolk LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        WMI05 Columbus OH LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        2525 N Woodlawn Vstrm Wichita KS LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        Corning Big Flats LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        OB Crenshaw SPE GP LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        OB Crenshaw GCC LP, a Delaware limited partnership controlled by its general partner, OB Crenshaw SPE GP LLC.

        HMBF05 Newburyport MA LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        YorkTC05 Eatontown NJ LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        STI05 Franklin NJ LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        AFL05 Duncan SC Member LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        AFL05 Duncan SC LLC, a Delaware limited liability company controlled by its sole member, AFL05 Duncan SC Member LLC.

        MSI05-3 LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        WMI05 Hazelwood MO LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        CI05 Clintonville WI LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        PZ05 Maple Heights OH LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        YCC06 South Hadley MA LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        NW05 Richmond VA LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        SVMMC05 Toledo OH LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        ACI06 Champaign IL LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        UC06 Roseville MN LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

C-7

---

        TCI06 Burnsville MN LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        RC06 Menomonee Falls WI LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        SJMH06 Baytown TX GP LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        SJMH06 Baytown TX LP, a Delaware limited partnership controlled by its general partner, SJMH06 Baytown TX GP LLC.

        NJT06 Sterling Heights MI LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        CMS06-3 LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        MPI06 Mason OH LLC, a Delaware limited liability company, controlled by its manager, Gladstone Commercial Limited Partnership.

        GCC Chicago Holdings, LLC, a Delaware limited liability company, controlled by its manager, Gladstone Commercial Limited Partnership.

        AC07 Lawrenceville GA LLC, a Delaware limited liability company, controlled by its manager, Gladstone Commercial Limited Partnership.

        EE07 Raleigh NC GP LLC, a Delaware limited liability company, controlled by its manager, Gladstone Commercial Limited Partnership.

        EE07 Raleigh NC, L.P., a Delaware limited partnership, controlled by its general partner, EE07 Raleigh NC GP LLC.

        WPI07 Tulsa OK LLC, a Delaware limited liability company, controlled by its manager, Gladstone Commercial Limited Partnership.

        APML07 Hialeah FL LLC, a Delaware limited liability company, controlled by its manager, Gladstone Commercial Limited Partnership.

        EI07 Tewksbury MA LLC, a Delaware limited liability company, controlled by its manager, Gladstone Commercial Limited Partnership.

        GBI07 Syracuse NY LLC, a Delaware limited liability company, controlled by its manager, Gladstone Commercial Limited Partnership.

        CDLCI07 Mason OH LLC, a Delaware limited liability company, controlled by its manager, Gladstone Commercial Limited Partnership.

        FTCH107 Grand Rapids MI LLC, a Delaware limited liability company, controlled by its manager, Gladstone Commercial Limited Partnership.

        DBP107 Bolingbrook IL LLC, a Delaware limited liability company, controlled by its manager, Gladstone Commercial Limited Partnership.

        Pocono PA GCC GP LLC, a Delaware limited liability company, controlled by its manager, Gladstone Commercial Limited Partnership.

        RCOG07 Georgia LLC, a Delaware limited liability company, controlled by its manager Gladstone Commercial Limited Partnership.

        C08 Fridley MN LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

C-8

---

        SRFF08 Reading PA GP LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        SRFF08 Reading PA, L.P., a Delaware limited partnership controlled by its general partner, SRFF08 Reading PA GP LLC.

        OS08 Winchester VA LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        RB08 Concord OH LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        RPT08 Pineville NC GP LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        RPT08 Pineville NC L.P., a Delaware limited partnership controlled by its general partner, RPT08 Pineville NC GP LLC.

        FMCT08 Chalfont PA GP LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        FMCT08 Chalfont PA, L.P., a Delaware limited partnership controlled by its general partner, FMCT08 Chalfont PA GP LLC.

        D08 Marietta OH LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        ELF08 Florida LLC, a Delaware limited liability company controlled by its manager, Gladstone Commercial Limited Partnership.

        Gladstone Land Corporation, a Delaware corporation controlled by David Gladstone through indirect 100% stock ownership.

        Gladstone Land Partners, LLC, a Delaware limited liability company controlled by its manager, Gladstone Land Corporation.

        SC Land, Inc., a California corporation and wholly-owned subsidiary of Gladstone Land Limited Partnership.

        Gladstone Land Limited Partnership, a Delaware limited partnership controlled by its general partner, Gladstone Land Partners, LLC.

        San Andreas Road Watsonville LLC, a California limited liability company controlled by its manager, Gladstone Land Limited Partnership.

        West Gonzales Road Oxnard LLC, a California limited liability company controlled by its manager, Gladstone Land Limited Partnership.

        Gladstone Lending Corporation, a Maryland corporation controlled by David Gladstone through 100% indirect stock ownership.

        Gladstone Holding Corporation, a Delaware corporation controlled by David Gladstone through 100% indirect stock ownership.

        Gladstone Management Corporation, a Delaware corporation controlled by Gladstone Holding Corporation, through 100% ownership.

        Gladstone Administration, LLC, a Delaware limited liability company and wholly-owned subsidiary of Gladstone Holding Corporation.

        Gladstone Securities, LLC, a Connecticut limited liability company controlled by its member, Gladstone Holding Corporation.

C-9

---

        Gladstone General Partner, LLC, a Delaware limited liability company controlled by its manager, Gladstone Management Corporation.

        Gladstone Participation Fund LLC, a Delaware limited liability company controlled by Gladstone General Partner, LLC.

        Gladstone Partners Fund, LP, a Delaware limited partnership controlled by its general partner, Gladstone Management Corporation.

Item 29.    Number of Holders of Securities

        The following table sets forth the approximate number of record holders of our common stock at May 12, 2010.

Item 30.    Indemnification

        Subject to the Investment Company Act of 1940, as amended (the "1940 Act") or any valid rule, regulation or order of the Securities and Exchange Commission ("SEC") thereunder, our articles of incorporation and bylaws provide that we will indemnify any person who was or is a party or is threatened to be made a party to any threatened action, suit or proceeding whether civil, criminal, administrative or investigative, by reason of the fact that he is or was our director or officer, or is or was serving at our request as a director, officer, partner or trustee of another corporation, real estate investment trust, partnership, joint venture, trust, employee benefit plan or other enterprise to the maximum extent permitted by Section 2-418 of the Annotated Code of Maryland, Corporations and Associations (the "Maryland Law"). The 1940 Act provides that a company may not indemnify any director or officer against liability to it or its security holders to which he or she might otherwise be subject by reason of his or her willful misfeasance, bad faith, gross negligence or reckless disregard of the duties involved in the conduct of his or her office unless a determination is made by final decision of a court, by vote of a majority of a quorum of directors who are disinterested, non-party directors or by independent legal counsel that the liability for which indemnification is sought did not arise out of the foregoing conduct. In addition to any indemnification to which our directors and officers are entitled pursuant to our articles of incorporation and bylaws and Maryland Law, our articles of incorporation and bylaws permit us to indemnify our other employees and agents to the fullest extent permitted by Maryland Law, whether such employees or agents are serving us or, at our request, any other entity.

        In addition, the investment advisory and management agreement between us and our investment adviser, Gladstone Management Corporation (the "Adviser"), as well as the administration agreement between us and our administrator Gladstone Administration, LLC (the "Administrator"), each provide that, absent willful misfeasance, bad faith, or gross negligence in the performance of their respective duties or by reason of the reckless disregard of their respective duties and obligations, our Adviser or our Administrator, as applicable, and their respective officers, managers, partners, agents, employees, controlling persons, members, and any other person or entity affiliated with it are entitled to indemnification from us for any damages, liabilities, costs, and expenses (including reasonable attorneys' fees and amounts reasonably paid in settlement) arising from the rendering of our Adviser's services under the investment advisory and management agreement or otherwise as our investment adviser, or the rendering of our Administrator's services under the administration agreement, as applicable.

C-10

---

Item 31.    Business and Other Connections of Investment Adviser

        A description of any other business, profession, vocation or employment of a substantial nature in which our Adviser, and each director or executive officer of our Adviser, is or has been during the past two fiscal years, engaged in for his or her own account or in the capacity of director, officer, employee, partner or trustee, is set forth in Part A of this Registration Statement in the section entitled "Management." Additional information regarding our Adviser and its officers and directors is set forth in its Form ADV, as filed with the SEC, and is incorporated herein by reference.

Item 32.    Location of Accounts and Records

        All accounts, books or other documents required to be maintained by Section 31(a) of the 1940 Act and the rules thereunder are maintained at the offices of:

(1)

the Registrant, Gladstone Capital Corporation, 1521 Westbranch Drive, Suite 200, McLean, VA 22102;



(2)

the Transfer Agent, BNY Mellon Shareowner Services, 480 Washington Boulevard, Jersey City, NJ 07310;



(3)

the Adviser, Gladstone Management Corporation, 1521 Westbranch Drive, Suite 200, McLean, VA 22102;



(4)

the Custodian, The Bank of New York Mellon Corp., 2 Hanson Place, Sixth Floor, Brooklyn, NY 11217; and



(5)

the Collateral Custodian, The Bank of New York Mellon Corp., 2 Hanson Place, Sixth Floor, Brooklyn, NY 11217.

Item 33.    Management Services

        Not applicable.

Item 34.    Undertakings

1.

We hereby undertake to suspend the offering of shares until the prospectus is amended if, subsequent to the effective date of this registration statement, our net asset value declines more than ten percent from our net asset value as of the effective date of this registration statement.

2.

We hereby undertake:

(a)

to file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

(i)

to include any prospectus required by Section 10(a)(3) of the Securities Act of 1933, as amended, or the Securities Act;

(ii)

to reflect in the prospectus any facts or events arising after the effective date of this registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement; and

(iii)

to include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement.

(b)

that, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of those securities at that time shall be deemed to be the initial bona fide offering thereof;

C-11

---

(c)

to remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering; and



(d)

that, for the purpose of determining liability under the Securities Act to any purchaser, if the Registrant is subject to Rule 430C: Each prospectus filed pursuant to Rule 497(b), (c), (d) or (e) under the Securities Act as part of a registration statement relating to an offering, other than prospectuses filed in reliance on Rule 430A under the Securities Act, shall be deemed to be part of and included in the registration statement as of the date it is first used after effectiveness. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such first use, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such date of first use;



(e)

that for the purpose of determining liability of the Registrant under the Securities Act to any purchaser in the initial distribution of securities: The undersigned Registrant undertakes that in a primary offering of securities of the undersigned Registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned Registrant will be a seller to the purchaser and will be considered to offer or sell such securities to the purchaser:



(i)

any preliminary prospectus or prospectus of the undersigned Registrant relating to the offering required to be filed pursuant to Rule 497 under the Securities Act;



(ii)

the portion of any advertisement pursuant to Rule 482 under the Securities Act relating to the offering containing material information about the undersigned Registrant or its securities provided by or on behalf of the undersigned Registrant; and



(iii)

any other communication that is an offer in the offering made by the undersigned Registrant to the purchaser.



(f)

To file a post-effective amendment to the registration statement, and to suspend any offers or sales pursuant the registration statement until such post-effective amendment has been declared effective under the Securities Act, in the event the shares of the Registrant are trading below its net asset value and either (i) the Registrant receives, or has been advised by its independent registered accounting firm that it will receive, an audit report reflecting substantial doubt regarding the Registrant's ability to continue as a going concern or (ii) the Registrant has concluded that a material adverse change has occurred in its financial position or results of operations that has caused the financial statements and other disclosures on the basis of which the offering would be made to be materially misleading.

3.

We hereby undertake that:

(a)

for the purpose of determining any liability under the Securities Act, the information omitted from the form of prospectus filed as part of this registration statement in reliance upon Rule 430A and contained in a form of prospectus filed by us under Rule 497(h) under the Securities Act shall be deemed to be part of this registration statement as of the time it was declared effective; and

(b)

for the purpose of determining any liability under the Securities Act, each post-effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of the securities at that time shall be deemed to be the initial bona fide offering thereof.

C-12

---

SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Registrant has duly caused this Post-Effective Amendment No. 1 to the Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of McLean and Commonwealth of Virginia, on the 17th day of May 2010.

        Pursuant to the requirements of the Securities Act of 1933, as amended, this Post-Effective Amendment No. 1 to the Registration Statement has been signed below by the following persons in the capacities indicated on May 17, 2010:

C-13

---

C-14

---

Exhibit List

C-15

---

C-16

---

QuickLinks

EXPLANATORY NOTE
Part C—OTHER INFORMATION

Item 25. Financial Statements and Exhibits

GLADSTONE CAPITAL CORPORATION INDEX TO CONSOLIDATED FINANCIAL STATEMENTS

Item 26. Marketing Arrangements
Item 27. Other Expenses of Issuance and Distribution
Item 28. Persons Controlled by or Under Common Control
Item 29. Number of Holders of Securities
Item 30. Indemnification
Item 31. Business and Other Connections of Investment Adviser
Item 32. Location of Accounts and Records
Item 33. Management Services
Item 34. Undertakings

SIGNATURES