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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 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): September 23, 2025

COPT DEFENSE PROPERTIES

(Exact name of registrant as specified in its charter)

Maryland |  | 1-14023 |  | 23-2947217
(State or other jurisdiction |  | (Commission File |  | (IRS Employer
of incorporation) |  | Number) |  | Identification No.)

6711 Columbia Gateway Drive, Suite 300, Columbia, MD | 21046
(Address of principal executive offices) | (Zip Code)

Registrant’s telephone number, including area code: (443) 285-5400

Not applicable

(Former name or former address, if changed since last report.)

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):

¨ | Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
¨ | Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
¨ | Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
¨ | Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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

Title of each class |  | Trading Symbol(s) |  | Name of each exchange on which registered
Common Shares of beneficial interest, $0.01 par value |  | CDP |  | New York Stock Exchange

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. ¨

Item 8.01. | Other Events

COPT Defense Properties is filing this Current Report on Form 8-K solely in order to file as an exhibit hereto certain operating and financial information.

Item 9.01. | Financial Statements and Exhibits

(d) | Exhibits.

Exhibit Number |  | Exhibit Title
99.1 |  | COPT Defense Properties Supplemental Operating and Financial Information.
104 |  | Cover Page Interactive Data File (embedded within the Inline XBRL document).

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.

|  | COPT DEFENSE PROPERTIES
|  | /s/ Anthony Mifsud
|  | Anthony Mifsud
|  | Executive Vice President and Chief Financial Officer
| Date: | September 23, 2025