Exhibit 5.1

CLIFFORD CHANCE US LLP

31 WEST 52ND STREET

NEW YORK, NY 10019-6131

TEL +1 212 878 8000

FAX +1 212 878 8375

www.cliffordchance.com

April 20, 2018

Apollo Commercial Real Estate Finance, Inc.

c/o Apollo Global Management, LLC

9 West 57th Street, 43rd Floor

New York, NY 10019

Ladies and Gentlemen:

We have acted as counsel to Apollo Commercial Real Estate Finance, Inc., a Maryland corporation (the “Company”), in connection with a registration statement on Form S-3 (File No. 333-214478), as amended (the “Registration Statement”), filed by the Company with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”). We are furnishing this letter to you in connection with the registration for resale from time to time by the selling stockholders named in the section entitled “Selling Stockholders” in the Registration Statement of up to 10,493,529 shares of the Company’s common stock, par value $0.01 per share (the “Common Stock”), and 6,770,393 shares of the Company’s 8.00% Fixed-to-Floating Series B Cumulative Redeemable Perpetual Preferred Stock, par value $0.01 per share (the “Series B Preferred Stock” and, together with the Common Stock, the “Securities”).

In rendering the opinion expressed below, we have examined and relied upon originals or copies, certified or otherwise identified to our satisfaction, of such corporate records, documents, certificates and other instruments as in our judgment are necessary or appropriate. As to factual matters relevant to the opinion set forth below, we have relied upon certificates of officers of the Company and public officials.

Based on the foregoing, and such other examination of law as we have deemed necessary, we are of the opinion that the Securities have been legally issued and are fully paid and nonassessable.

The opinion set forth in this letter relates only to the Maryland General Corporation Law. We express no opinion as to the laws of another jurisdiction and we assume no responsibility for the applicability, or effect of the law of any other jurisdiction.

We consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement and to the reference to us under the caption “Legal Matters” in the prospectus, which is a part of the Registration Statement. In giving this consent, we do not concede that we are within the category of persons whose consent is required under the Securities Act or the rules and regulations of the Commission promulgated thereunder.

Very truly yours,

/s/ Clifford Chance US LLP