MDCA MDC Partners Inc

Get informed before you vote *If you choose to vote these shares in person at the meeting, you must request a “legal proxy.” To do so, please follow the instructions at www.ProxyVote.com or request a paper copy of the materials, which will contain the appropriate instructions. 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 Your Vote Counts! FLASHID-JOB# For complete information and to vote, visit www.ProxyVote.com Control # Ricky Campana P.O. Box 123456 Suite 500 51 Mercedes Way Edgewood, NY 11717 148,294 322,224 1 OF 2 30# Hextone, Inc. P.O. Box 9142 Farmingdale, NY 11735 XXXX XXXX XXXX XXXX STAGWELL INC. 2023 Annual Meeting Vote by June 13, 2023 11:59 PM ET You invested in STAGWELL 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 material for the shareholder meeting to be held on June 14, 2023. View the Notice & Proxy Statement, Annual Report online OR you can receive a free paper or email copy of the material(s) by requesting prior to May 31, 2023. If you would like to request a copy of the material(s) for this and/or future shareholder 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 in Person at the Meeting* June 14, 2023 11:30 AM EDT STAGWELL INC. One World Trade Center, Floor 65 New York, NY 10007

Voting Items Board Recommends THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming shareholder meeting. Please follow the instructions on the reverse side to vote these important matters. Vote at www.ProxyVote.com FLASHID-JOB# Control # XXXX XXXX XXXX XXXX 1.00000 322,224 148,294 Under New York Stock Exchange rules, brokers may vote “routine” matters at their discretion if your voting instructions are not communicated to us at least 10 days before the meeting. We will nevertheless follow your instructions, even if the broker’s discretionary vote has already been given, provided your instructions are received prior to the meeting date. STAGWELL INC. 2023 Annual Meeting Vote by June 13, 2023 11:59 PM ET 1. Election of Directors Nominees: 01 Charlene Barshefsky 04 Mark J. Penn 07 Irwin D. Simon 02 Bradley J. Gross 05 Desirée Rogers 08 Rodney Slater 03 Wade Oosterman 06 Eli Samaha 09 Brandt Vaughan For 2 Approval of 2023 Employee Stock Purchase Plan. For 3 Approval, on an advisory basis, of 2022 compensation of our named executive officers. For 4 Advisory vote on frequency of future advisory votes on executive compensation. Year 5 Ratification of selection of PricewaterhouseCoopers LLP as independent registered public accounting firm for the fiscal year ending December 31, 2023. For NOTE: Such other business as may properly come before the meeting or any adjournment thereof.