Sec Form 3 Filing - LEONARD WILLIAM P @ Greenbrook TMS Inc. - 2024-01-01

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP 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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1. Name and Address of Reporting Person LEONARD WILLIAM P 2. Issuer Name and Ticker or Trading Symbol Greenbrook TMS Inc. [ GBNH] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) President and CEO (Last) (First) (Middle) C/O GREENBROOK 890 YONGE STREET, 7TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 01/01/2024 (Street) TORONTO, A6M4W3P4 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Shares 832,500 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Options $ 10.13 ( 2 ) ( 1 ) 02/03/2030 Common Shares 10,000 D Options $ 0.75 ( 3 ) 05/15/2033 Common Shares 100,000 D Performance Share Units $ 0 ( 5 ) 12/31/2023( 4 ) 03/15/2024 Common Shares 3,865 D Subordinated Convertible Notes ( 6 ) ( 9 ) 08/28/2023 ( 7 ) Common Shares 184,502 ( 8 ) D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other LEONARD WILLIAM P C/O GREENBROOK 890 YONGE STREET 7TH FLOOR TORONTO, A6M4W3P4 X President and CEO Signatures /s/William Leonard 01/02/2024 Signature of Reporting Person Date

Explanation of Responses:

( 1 )These options were granted pursuant to the Company's Amended Employee Stock Option Plan, as described in the Company's 2022 Meeting Information Circular, filed with the Securities and Exchange Commission on May 23, 2023. The options were granted on February 3, 2020 and vested over a three year period, with one-third vesting on each of the 3 anniversaries of the date of the grant. As of the date hereof, all options are vested and exercisable. ( 2 )Converted to USD based on the average daily exchange rate of the Bank of Canada reported on December 29, 2023. Each option may be exercised for a price of $13.40 Canadian dollars. ( 3 )These options were granted pursuant to the Company's Omnibus Equity Incentive Plan (the "Equity Incentive Plan"), as described in the Company's 2022 Meeting Information Circular, filed with the Securities and Exchange Commission on May 23, 2023, on May 15, 2023. Half of the options granted immediately vested while the remaining half vest over a two-year period, with one-quarter of the total amount vesting on each of the 2 anniversaries of the date of the grant. As of the date hereof, 50,000 options are vested and exercisable. ( 4 )These performance share units were granted pursuant to the Equity Incentive Plan, by the Company on August 5, 2021. The performance share units vested on December 31, 2023 after the attainment of certain performance vesting conditions relating to strategic initiatives. ( 5 )The performance share units are to be settled in cash on or before March 15, 2024. The total cash award will be equivalent to the closing price of the Common Shares covered by the performance share unit on the date of settlement. ( 6 )On August 28, 2023, Mr. Leonard acquired from the Company, upon exchange on a private placement basis of previously-held Company-issued notes, an aggregate principal amount of $40,000 of the Company's subordinated convertible promissory notes (the "Subordinated Convertible Notes"). ( 7 )The latest date that the Subordinated Convertible Notes can mature is March 31, 2028. ( 8 )The number of shares issuable upon conversion of the Subordinated Convertible Note is calculated by multiplying the Reference Conversion Price (as defined in footnote 9) by the aggregate principal amount of Mr. Leonard's Subordinated Convertible Notes. ( 9 )The Subordinated Convertible Notes are convertible at a price equal to the lesser of (a) 85% of the closing price per Common Shares on Nasdaq or any other market as of the closing date for such Subordinated Convertible Notes (the "Reference Conversion Price") with the Reference Conversion Price in effect as of January 2, 2024 being $0.2168 and (b)(i) 85% of the 30-day volume weighted average trading price of the Common Shares prior to conversion, or (ii) if the Common Shares are not listed on any of Nasdaq or another trading market at the time of conversion, a per share price based equal to 85% of the fair market value per Common Share as of such date; provided, that, in any event, the Subordinated Convertible Note conversion price shall not be lower than $0.078. The Subordinated Convertible Notes conversion price is also subject to customary anti-dilution adjustments.

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