As filed with the Securities and Exchange Commission on February 13, 2019

1933 Act File No. 333-228720

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

Form N-2

GLADSTONE CAPITAL CORPORATION

(Exact name of registrant as specified in charter)

1521 Westbranch Drive, Suite 100

McLean, Virginia 22102

Address of Principal Executive Offices (Number, Street, City, State, Zip Code)

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 (Number, Street, City, State, Zip Code) of Agent For Service

COPIES TO:

William J. Tuttle

Nicole M. Runyan

Erin M. Lett

Proskauer Rose LLP

1001 Pennsylvania Avenue NW

Suite 600 South

Washington, D.C. 20004

Tel: (202) 416-6800

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, other than securities offered in connection with a dividend reinvestment plan, check the following box.  ☒

It is proposed that this filing will become effective (check appropriate box):

EXPLANATORY NOTE

This Post-Effective Amendment No. 1 to the Registration Statement on Form N-2 (File No. 333-228720) (the “Registration Statement”) of Gladstone Capital Corporation (the “Company” or the “Registrant”) 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 additional exhibits to such 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

1. Financial Statements

The following financial statements and schedule 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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The information contained under the heading “Plan of Distribution” on page 147 of the prospectus is incorporated herein by reference, and any information concerning any underwriters will be contained in the accompanying prospectus supplement, if any.

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

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, 2018:

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 the Adviser, Gladstone Management Corporation. We may also be deemed to be under “common control” with Gladstone Lending Corporation, a Maryland Corporation, and Gladstone Participation Fund, LLC, a Delaware limited liability company, because 100% of the voting securities of each are owned by the Adviser.

The following table sets forth the approximate number of record holders of each class of our securities at December 3, 2018. This number does not include stockholders for whom shares are held in “street name.”

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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 (“MGCL”) 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:

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.

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 if our board of directors determines that such person acted in good faith and in a manner reasonably believed to be in or not

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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. However, our bylaws permit us to advance expenses only 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.

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.

Insofar as indemnification for liability arising under the Securities Act of 1933, as amended (the “Securities Act”), may be permitted to directors, officers and controlling persons of the Registrant pursuant to the foregoing provisions, or otherwise, the Registrant has been advised that, in the opinion of the U.S. Securities and Exchange Commission, such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

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.

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:

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Not applicable.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, 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 13th day of February, 2019.

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 February 13, 2019: