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. )

Filed by the Registrant x

Filed by a Party other than the Registrant ¨

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

x Definitive Additional Materials

¨ Soliciting Material Pursuant to §240.14a-12

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

SCHOLAR ROCK HOLDING CORPORATION

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

x 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! SCHOLAR ROCK HOLDING CORPORATION 301 BINNEY STREET 3RD FLOOR CAMBRIDGE, MA 02142 SCHOLAR ROCK HOLDING CORPORATION 2022 Annual Meeting Vote by May 25, 2022 11:59 PM ET You invested in SCHOLAR ROCK HOLDING CORPORATION 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 material for the stockholder meeting to be held on May 26, 2022. *Please check the meeting materials for any special requirements for meeting attendance. Smartphone users Point your camera here and vote without entering a control number V1.1 For complete information and to vote, visit www.ProxyVote.com Control # D77598-P71847 Get informed before you vote View the Notice of Internet Availability of Proxy Materials, Proxy Statement and Annual Report online OR you can receive a free paper or email copy of the material(s) by requesting prior to May 12, 2022. 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. Vote Virtually at the Meeting* May 26, 2022 9:00 AM, Eastern Time Virtually at: www.virtualshareholdermeeting.com/SRRK2022

THIS IS NOT A VOTABLE BALLOT Your vote is important. We encourage you to vote in advance even if you plan to attend the 2022 Annual Meeting online. This is an overview of the proposals being presented at the upcoming stockholder meeting. Please follow the instructions on the reverse side to vote these important matters. If shares are held in multiple accounts, please vote on each proxy card you receive to ensure that all of the shares are represented at the 2022 Annual Meeting. Vote at www.ProxyVote.com Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Sign up for E-delivery”. Voting Items Board Recommends D77599-P71847 01) Nagesh K. Mahanthappa, Ph.D. 02) Joshua Reed 1. To elect two Class I Directors, each to serve until the 2025 annual meeting of stockholders and until his successor has been duly elected and qualified. Nominees: 2. To ratify the appointment of Ernst & Young LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2022. NOTE: Such other business as may properly come before the meeting or any adjournment thereof. For For