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): August 11, 2021

CORPORATE OFFICE PROPERTIES TRUST

(Exact name of registrant as specified in its charter)

6711 Columbia Gateway Drive, Suite 300

Columbia, Maryland 21046

(Address of principal executive offices)

(443) 285-5400

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

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 (see General Instruction A.2 below):

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

On August 11, 2021, Corporate Office Properties, L.P. (“COPLP”), the operating partnership of Corporate Office Properties Trust (“COPT”), consummated the offering of $400,000,000 aggregate principal amount of its 2.000% Senior Notes due 2029 (the “Notes”). The Notes will be fully and unconditionally guaranteed by COPT. The Notes were offered pursuant to an effective shelf registration statement on Form S-3 (File Nos. 333-230764 and 333-230764-01) filed by COPT and COPLP with the Securities and Exchange Commission on April 8, 2019 (the “Registration Statement”), including a base prospectus, dated April 8, 2019, and a prospectus supplement, dated August 2, 2021, filed with the Securities and Exchange Commission on August 4, 2021.

The terms of the Notes are governed by a senior indenture, dated as of April 8, 2019, by and among COPLP, as issuer, COPT, as guarantor, and U.S. Bank National Association, as trustee (the “Base Indenture”), as supplemented and amended by a third supplemental indenture thereto, dated as of August 11, 2021 (the “Third Supplemental Indenture,” and together with the Base Indenture, the “Indenture”).

A copy of the Base Indenture was previously filed as Exhibit 4.1 to the Registration Statement and is incorporated by reference herein. The Third Supplemental Indenture is filed as Exhibit 4.2 hereto.

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.