6-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K

Report of Foreign Private Issuer Pursuant to Rule 13a-16 or 15d-16 under the Securities Exchange Act of 1934

For the month of December 2025

Commission File Number 001-37626

Mesoblast Limited

(Exact name of Registrant as specified in its charter)

Not Applicable

(Translation of Registrant’s name into English)

Australia (Jurisdiction of incorporation or organization)

Silviu Itescu

Chief Executive Officer and Executive Director

Level 38

55 Collins Street

Melbourne 3000

Australia

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F:

Form 20-F ☑ Form 40-F ☐

INFORMATION CONTAINED ON THIS REPORT ON FORM 6-K

On December 23, 2025, Mesoblast Limited filed with the Australian Securities Exchange a new issue announcement, change of director’s interest notice (Appendix 3Y) which is attached hereto as Exhibit 99.1, and is incorporated herein by reference.

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, thereunto duly organized.

Dated: December 24, 2025

INDEX TO EXHIBITS

exhibit991app3y-gregoryg

Gregory George Rule 3.19A.2 Appendix 3Y Change of Director’s Interest Notice Information or documents not available now must be given to ASX as soon as available. Information and documents given to ASX become ASX’s property and may be made public. Introduced 30/09/01 Amended 01/01/11 Name of entity MESOBLAST LIMITED ABN 68 109 431 870 We (the entity) give ASX the following information under listing rule 3.19A.2 and as agent for the director for the purposes of section 205G of the Corporations Act. Name of Director Gregory George Date of last notice 12 September 2025 Part 1 - Change of director’s relevant interests in securities In the case of a trust, this includes interests in the trust made available by the responsible entity of the trust Note: In the case of a company, interests which come within paragraph (i) of the definition of “notifiable interest of a director” should be disclosed in this part. Direct or indirect interest Direct and indirect Nature of indirect interest (including registered holder) Note: Provide details of the circumstances giving rise to the relevant interest. JP Morgan Nominees Australia Pty Limited (Interest in ordinary shares held in the form of American Depositary Shares (“ADS”) held by custodian JP Morgan Nominees Australia Pty Limited.) Each ADS represents a beneficial interest in 10 ordinary shares. Certain shares and ADSs held by G to the Fourth Investments, LLC which is controlled by Gregory George. Certain ADSs held by James George and Grant George, who have given power of attorney to Gregory George in respect of those ADSs. Date of change 17 December 2025 No. of securities held prior to change Direct 5 ordinary shares 12,829,328 ADSs. 200,000 warrants convertible into ADS. Indirect 9,640,077 ordinary shares. 12,908,777 ADS. 6,830,602 warrants to acquire ordinary shares. Class See above

Appendix 3Y Change of Director’s Interest Notice + See chapter 19 for defined terms. 01/01/2011 Appendix 3Y Page 2 3445-3578-7845, v. 1 Number acquired 4,000,000 warrants to acquire ordinary shares (or the applicable number of ADS at the holder’s election). In addition, since the most recent Appendix 3Y some of the ordinary shares in which Gregory George had a direct and indirect interest have been transmuted into ADSs on a 10 to 1 basis. This transmutation did not involve a change in Dr George’s notifiable interest in the underlying shares, and so did not require a separate Appendix 3Y. The numbers of shares and ADSs stated above reflect Dr George’s direct and indirect interests in shares and ADSs immediately prior to the acquisition of the new warrants. Number disposed Nil Value/Consideration Note: If consideration is non-cash, provide details and estimated valuation Nil (warrants issued as partial commitment fee for convertible note facility, and approved by shareholders 25 November 2025). No consideration payable to transmute shares into ADSs (no change in beneficial interest in the underlying shares). No. of securities held after change Direct 5 ordinary shares 12,829,328 ADSs. 200,000 warrants convertible into ADS. 4,000,000 warrants to acquire ordinary shares (or the applicable number of ADS at the holder’s election). Indirect 9,640,077 ordinary shares. 12,908,777 ADS. 6,830,602 warrants to acquire ordinary shares Nature of change Example: on-market trade, off-market trade, exercise of options, issue of securities under dividend reinvestment plan, participation in buy-back Warrants issued as partial commitment fee for convertible note facility, as noted above. Part 2 – Change of director’s interests in contracts Note: In the case of a company, interests which come within paragraph (ii) of the definition of “notifiable interest of a director” should be disclosed in this part. Detail of contract N/A Nature of interest

Appendix 3Y Change of Director’s Interest Notice + See chapter 19 for defined terms. 01/01/2011 Appendix 3Y Page 3 3445-3578-7845, v. 1 Name of registered holder (if issued securities) Date of change No. and class of securities to which interest related prior to change Note: Details are only required for a contract in relation to which the interest has changed Interest acquired Interest disposed Value/Consideration Note: If consideration is non-cash, provide details and an estimated valuation Interest after change Part 3 – +Closed period Were the interests in the securities or contracts detailed above traded during a +closed period where prior written clearance was required? No If so, was prior written clearance provided to allow the trade to proceed during this period? If prior written clearance was provided, on what date was this provided?