Ownership Submission
FORM 3
 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
  Stagwell Agency Holdings LLC
 2. Date of Event Requiring Statement (Month/Day/Year)
03/14/2019		 3. Issuer Name and Ticker or Trading Symbol
MDC PARTNERS INC [MDCA]
(Last)
(First)
(Middle)
C/O THE STAGWELL GROUP LLC, 1808 EYE STREET, NW, SIXTH FLOOR		 4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

WASHINGTON, DC 20006		 6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security
(Instr. 4)		 2. Amount of Securities Beneficially Owned
(Instr. 4)		 3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)		 4. Nature of Indirect Beneficial Ownership
(Instr. 5)
Class A Subordinate Voting Shares 14,285,714
I
See Footnotes (1) (2)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)		 2. Date Exercisable and Expiration Date
(Month/Day/Year)		 3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)		 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)		 6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares
Series 6 convertible preference shares   (3)   (3) Class A Subordinate Voting Shares 10,000,000 (3) $ 5 (3) I See Footnotes (1) (2)

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
Stagwell Agency Holdings LLC
C/O THE STAGWELL GROUP LLC
1808 EYE STREET, NW, SIXTH FLOOR
WASHINGTON, DC 20006		     X    
Stagwell Group LLC
1808 EYE STREET, NW, SIXTH FLOOR
WASHINGTON, DC 20006		     X    
Penn Mark Jeffery
C/O THE STAGWELL GROUP LLC
1808 EYE STREET, NW, SIXTH FLOOR
WASHINGTON, DC 20006		   X   X   Chief Executive Officer  

Signatures

STAGWELL AGENCY HOLDINGS LLC, By: The Stagwell Group LLC, its manager, /s/ Mark J. Penn, Manager 03/26/2019
**Signature of Reporting Person Date
THE STAGWELL GROUP LLC, /s/ Mark J. Penn, Manager 03/26/2019
**Signature of Reporting Person Date
/s/ Mark J. Penn 03/26/2019
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) These securities are held directly by Stagwell Agency Holdings LLC ("SAH"). The Stagwell Group LLC is the manager of SAH. Mark J. Penn is the controlling person of The Stagwell Group LLC.
(2) Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein, except to the extent of such Reporting Person's pecuniary interest therein. The filing of this statement shall not be deemed to be an admission that, for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or otherwise, the Reporting Persons are the beneficial owners of any securities reported herein.
(3) The number of Class A Subordinate Voting Shares ("Class A Shares") of MDC Partners Inc. (the "Issuer") deliverable upon conversion of each Series 6 convertible preference shares of the Issuer (the "Preference Shares") is equal to the then-applicable liquidation preference divided by the then-applicable conversion price at such time. The initial liquidation preference of each Preference Share is $1,000. The initial conversion price is $5.00 per Preference Share, subject to customary anti-dilution adjustments. The liquidation preference of the Preference Shares accretes at 8.0% per annum, compounded quarterly until March 14, 2024. Holders of the Preference Shares are entitled to dividends in an amount equal to any dividends that would have been payable on the Class A Shares issuable upon conversion of the Preference Shares. Beginning two years after the Issue Date, the Issuer may redeem the Preferred Stock if certain conditions are met.
 
Remarks:
Effective as of March 18, 2019, Mark J. Penn became the chief executive officer and a director of the Issuer.

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