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As filed with the Securities and Exchange Commission on May 15, 2014

Securities Act File No. 333-185191

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM N-2

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Pre-Effective Amendment No.

x Post-Effective Amendment No. 3

GLADSTONE CAPITAL CORPORATION

(Exact Name of Registrant as Specified in Charter)

1521 Westbranch Drive, Suite 100

McLean, Virginia 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 100

McLean, Virginia 22102

(Name and Address of Agent For Service)

Copies to:

Lori B. Morgan

Bass, Berry & Sims PLC

150 Third Avenue

Suite 2800

Nashville, Tennessee 37201

Tel: (615) 742-6200

Fax: (615) 742-6293

Approximate Date of Proposed Public Offering: From time to time after the effective date of the 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, other than securities offered in connection with a dividend reinvestment plan, check the following box.  x

This filing will become effective immediately upon filing pursuant to Rule 462(d) under the Securities Act of 1933, as amended.  x

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EXPLANATORY NOTE

This Post-Effective Amendment No. 3 to the Registration Statement on Form N-2 (File No. 333-185191) 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 adding additional exhibits to such Registration Statement. Accordingly, this Post-Effective Amendment No. 3 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. 3 does not modify any other part of the Registration Statement. Pursuant to Rule 462(d) under the Securities Act, this Post-Effective Amendment No. 3 shall become effective immediately upon filing with the Securities and Exchange Commission. The contents of the Registration Statement are hereby incorporated by reference.

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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

2. Exhibits

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Item 26. Marketing Arrangements

The information contained under the heading “Plan of Distribution” on page 121 of the prospectus is incorporated herein by reference, and any information concerning any underwriters will be contained in the accompanying prospectus supplement, if any.

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

The following list sets forth each of the companies considered to be “controlled” by the Registrant as defined by the Investment Company Act of 1940, as of December 31, 2013:

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We may also be deemed to be under “common control” with the following entities: Gladstone Commercial Corporation; Gladstone Land Corporation; and Gladstone Investment Corporation by virtue of the fact that they are advised by our Adviser, Gladstone Management Corporation, as well as Gladstone Lending Corporation and Gladstone Participation Fund, LLC because 100% of the voting securities of each are owned by Gladstone Management Corporation.

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Item 29. Number of Holders of Securities

The following table sets forth the approximate number of record holders of each class of our securities at May 13, 2014. This number does not include stockholders for whom shares are held in “street name.”

Item 30. Indemnification

Indemnification and Limitation of Liability of Directors and Officers

Maryland law permits a Maryland corporation to include in its charter a provision limiting the liability of its directors and officers to the corporation and its stockholders for money damages, except for liability resulting from (a) actual receipt of an improper benefit or profit in money, property or services or (b) active and deliberate dishonesty that is established by a final judgment and is material to the cause of action. Our charter contains a provision that eliminates the liability of our directors and officers to the maximum extent permitted by Maryland law.

The Maryland General Corporation Law requires us (unless our charter provides otherwise, which our charter does not) to indemnify a director or officer who has been successful, on the merits or otherwise, in the defense of any proceeding to which he or she is made a party by reason of his or her service in that capacity. The MGCL permits us to indemnify our present and former directors and officers, among others, against judgments, penalties, fines, settlements and reasonable expenses actually incurred by them in connection with any proceeding to which they may be made or threatened to be made a party by reason of their service in those or other capacities unless it is established that:

Under the MGCL, we may not indemnify a director or officer in a suit by us or on our behalf in which the director or officer was adjudged liable to us or in a suit in which the director or officer was adjudged liable on the basis that personal benefit was improperly received. A court may order indemnification if it determines that the director or officer is fairly and reasonably entitled to indemnification, even though the director or officer did not meet the prescribed standard of conduct or was adjudged liable on the basis that personal benefit was improperly received. However, indemnification for an adverse judgment in a suit by us or on our behalf, or for a judgment of liability on the basis that personal benefit was improperly received, is limited to expenses.

In addition, the MGCL permits us to advance reasonable expenses to a director or officer upon our receipt of:

Our bylaws permit us to advance expenses so long as, in addition to the requirements above, we obtain security for the advance from the director or officer, we obtain insurance against losses arising by reason of lawful advances or we determine that there is reason to believe that the director or officer will be found entitled to 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 charter obligates us, to the maximum extent permitted by Maryland law in effect from time to time, to indemnify and pay or reimburse reasonable expenses in advance of final disposition of a proceeding to any director or officer, whether serving our company or at our request any other entity. Our charter also permits us to indemnify and advance expenses to any employee or agent of our company to the extent authorized by our board of directors or the bylaws and permitted by law.

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Our bylaws obligate us, to the maximum extent required by Maryland law or the charter, to 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, officer, employee or agent, or is or was serving at our request as a director, officer, manager, partner, trustee, employee or agent of another corporation, partnership, joint venture, trust, employee benefit plan or other enterprise. Our bylaws also obligate us, to the maximum extent permitted by Maryland law, to indemnify the foregoing persons if our board of directors determines that such person acted in good faith and in a manner reasonably believed to be in or not opposed to the best interests of our company, and, in the case of any criminal action or proceeding, that such person had no reasonable cause to believe that such person’s conduct was unlawful.

These provisions on indemnification and limitation of liability are subject to the limitations of the 1940 Act that prohibit us from protecting any director or officer against any liability to us or our stockholders arising from willful misfeasance, bad faith, gross negligence or reckless disregard of the duties involved in the conduct of such person’s office.

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, the Adviser or the 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 the Adviser’s services under the investment advisory and management agreement or otherwise as our investment adviser, or the rendering of the Administrator’s services under the administration agreement, as applicable.

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 the Adviser, and each director or executive officer of the 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 the 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:

Item 33. Management Services

Not applicable.

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Item 34. Undertakings

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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 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 15^th day of May, 2014.

POWER OF ATTORNEY

Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed below by the following persons in the capacities indicated on May 15, 2014:

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EXHIBIT INDEX

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