Sec Form 4 Filing - Cavaness Joel D @ Arthur J. Gallagher & Co. - 2021-05-15

FORM 4 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 Cavaness Joel D 2. Issuer Name and Ticker or Trading Symbol Arthur J. Gallagher & Co. [ AJG] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Vice President (Last) (First) (Middle) 2850 GOLF ROAD 3. Date of Earliest Transaction (MM/DD/YY) 05/15/2021 (Street) ROLLING MEADOWS, IL60008-4002 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 Stock 05/15/2021 J( 1 ) 1,524.1 A $ 0 1,524.1 I By Spouse Common Stock (restricted) 05/15/2021 J( 1 ) 2,185 ( 2 ) ( 3 ) A $ 0 2,185 I By Spouse

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 Phantom Stock ( 4 ) 05/15/2021 J( 1 ) 963.2 ( 5 ) ( 6 ) ( 6 ) Common Stock 963.2 $ 0 963.2 I By Spouse Non-qualified Stock Option $ 43.71 05/15/2021 J( 1 ) 2,600 ( 7 ) 03/17/2023 Common Stock 2,600 $ 43.71 26,200 D Non-qualified Stock Option $ 56.86 05/15/2021 J( 1 ) 1,600 ( 7 ) 03/16/2024 Common Stock 1,600 $ 56.86 24,900 D Non-qualified Stock Option $ 70.74 05/15/2021 J( 1 ) 1,150 ( 7 ) 03/15/2025 Common Stock 1,150 $ 70.74 19,450 D Non-qualified Stock Option $ 79.59 05/15/2021 J( 1 ) 1,100 ( 7 ) 03/14/2026 Common Stock 1,100 $ 79.59 18,350 D Non-qualified Stock Option $ 86.17 05/15/2021 J( 1 ) 1,310 ( 7 ) 03/12/2027 Common Stock 1,310 $ 86.17 20,470 D Non-qualified Stock Option $ 127.9 05/15/2021 J( 1 ) 1,210 ( 7 ) 03/16/2028 Common Stock 1,210 $ 127.9 20,945 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Cavaness Joel D 2850 GOLF ROAD ROLLING MEADOWS, IL60008-4002 Vice President Signatures /s/ Seth Diehl, by power of attorney 05/18/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Deemed acquired due to marriage on May 15, 2021. ( 2 )Consists of 600 RSUs granted 3/16/2017; 500 RSUs granted 3/15/2018; 450 RSUs granted 3/14/2019; 440 RSUs granted 3/12/2020; and 195 RSUs granted 3/16/2021. ( 3 )Restricted stock unit award vesting five years after the date of grant. ( 4 )Each share of phantom stock represents a right to receive one share of Gallagher common stock. ( 5 )This award was granted in 2017 and vests on March 31, 2022. ( 6 )These shares represent awards under the Deferred Cash Participation Plan, a nonqualified deferred compensation plan of the Company, which have been deemed invested in Company common stock at the election of the participant. Participants vest in these awards on the fifth anniversary of the date of grant. ( 7 )One-third of this stock option becomes exerciseable on each of the 3rd, 4th, and 5th anniversaries of the grant date.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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