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 25, 2026

Innovative Industrial Properties, Inc.

(Exact name of registrant as specified in its charter)

1389 Center Drive, Suite 200

Park City, Utah 84098

(Address of principal executive offices, including zip code)

Registrant’s telephone number, including area code: (858) 997-3332

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):

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

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. ¨

Upon authorization of its board of directors, Innovative Industrial Properties, Inc. (the “Company”) filed Articles of Amendment (the “Articles of Amendment”) with the State Department of Assessments and Taxation of Maryland to amend the Company’s Second Articles of Amendment and Restatement (the “Charter”) to increase the total number of shares of stock that the Company has authority to issue from 100,000,000 shares to 175,000,000 shares, with the number of authorized shares of common stock, par value $0.001 per share, increasing from 50,000,000 to 100,000,000 and the number of authorized shares of preferred stock, par value $0.001 per share, increasing from 50,000,000 to 75,000,000, effective as of 12:01 a.m. Eastern Time on September 25, 2026. Under the Charter, the Company’s board of directors has the authority, without any action by the Company’s shareholders, to increase the number of shares of stock that the Company is authorized to issue.

A copy of the Articles of Amendment is attached hereto as Exhibit 3.1 and is incorporated herein by reference.

(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.