UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 OR 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported) June 21, 2013 (June 19, 2013)

Gladstone Commercial Corporation

(Exact name of registrant as specified in its charter)

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

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Item 8.01. Other Events.

On June 19, 2013, Gladstone Commercial Corporation (the “Company”), a Maryland corporation, and Gladstone Commercial Limited Partnership (the “Operating Partnership”), a Delaware limited partnership, entered into an underwriting agreement (the “Underwriting Agreement”) with Janney Montgomery Scott LLC (“Janney”), as representative of the several underwriters named in Schedule A annexed thereto (the “Underwriters”). Pursuant to the terms and conditions of the Underwriting Agreement, the Company agreed to sell 1,320,000 shares of its common stock, par value $0.001 per share, at a purchase price to the public of $18.82. Pursuant to the Underwriting Agreement, the Company granted the Underwriters a 30-day option to purchase up to an additional 198,000 shares of common stock to cover over-allotments, if any. The common stock was offered and sold pursuant to a prospectus supplement, dated June 19, 2013, and a base prospectus, dated September 27, 2010, relating to the Company’s effective shelf registration statement on Form S-3 (File No. 333-169290). The Company expects the transaction to close on June 24, 2013. Net proceeds from the offering will be approximately $23.5 million (or approximately $27.0 million if the Underwriters exercise their over-allotment option in full) after deducting the underwriting discounts and commissions and other estimated offering expenses payable by the Company.

The Underwriting Agreement contains customary representations, warranties and agreements by the Company, conditions to closing, indemnification rights and obligations of the parties and termination provisions. The description of the Underwriting Agreement set forth above is qualified by reference to the Underwriting Agreement, a copy of which is filed as Exhibit 1.1 to this Current Report on Form 8-K and is incorporated herein by reference.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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