UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No. )

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Check the appropriate box:

☐ Preliminary Proxy Statement

☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☐ Definitive Proxy Statement

☒ Definitive Additional Materials

☐ Soliciting Material Pursuant to §240.14a-12

BLACKSTONE MORTGAGE TRUST, INC.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if Other Than the Registrant)

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☒ No fee required

☐ Fee paid previously with preliminary materials

☐ Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11

Your Vote Counts! BLACKSTONE MORTGAGE TRUST, INC. 2024 Annual Meeting Vote in advance by June 20, 2024 11:59 PM Eastern Time [Graphic Appears Here] V48502-P09573 You invested in BLACKSTONE MORTGAGE TRUST, INC. and it’s time to vote! You have the right to vote on proposals being presented at the Annual Meeting. This is an important notice regarding the availability of proxy materials for the stockholder meeting to be held on June 21, 2024. Get informed before you vote View the Notice and Proxy Statement and Annual Report online at www.ProxyVote.com OR you can receive a free paper or email copy of the material(s) by requesting prior to June 7, 2024. If you would like to request a copy of the material(s) for this and/or future stockholder meetings, you may (1) visit www.ProxyVote.com, (2) call 1-800-579-1639 or (3) send an email to sendmaterial@proxyvote.com. If sending an email, please include your control number (indicated below) in the subject line. Unless requested, you will not otherwise receive a paper or email copy. For complete information and to vote, visit www.ProxyVote.com Control # Smartphone users Point your camera here and vote without entering a control number Vote in Person at the Meeting* June 21, 2024 9:00 AM Eastern Time at the offices of Simpson Thacher & Bartlett LLP 425 Lexington Avenue New York, New York 10017 *Please check the meeting materials for any special requirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares

. Vote at www.ProxyVote.com THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming stockholder meeting. We encourage you to access and review all of the important information contained in the proxy materials before voting. Please follow the instructions on the reverse side to vote these important matters. Board Voting Items Recommends 1. Election of Directors Nominees: For 01) Timothy S. Johnson 04) Thomas E. Dobrowski 07) Henry N. Nassau 02) Katharine A. Keenan 05) Nnenna Lynch 08) Gilda Perez Alvarado 03) Leonard W. Cotton 06) Michael B. Nash 09) Lynne B. Sagalyn 2. Ratify the appointment of Deloitte & Touche LLP as the Company’s independent registered public accounting firm for For the fiscal year ending December 31, 2024. 3. Advisory Vote on Executive Compensation: To approve in a non-binding, advisory vote, the compensation paid to our For named executive officers. NOTE: To consider and act upon any other matters which may properly come before the meeting or any adjournment or postponement thereof. Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Delivery Settings”.