Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 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 * Bialecki Andrew 2. Issuer Name and Ticker or Trading Symbol Klaviyo, Inc. [KVYO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director __X__ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Chief Executive Officer (Last) (First) (Middle) C/O KLAVIYO, INC., 125 SUMMER STREET, 6TH FLOOR 3. Date of Earliest Transaction (Month/Day/Year) 06/11/2025 (Street) BOSTON, MA 02110 4. If Amendment, Date Original Filed (Month/Day/Year) 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 (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 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 Series A Common Stock 06/11/2025 C 100,000 A (1)(2) 100,000 D Series A Common Stock 06/11/2025 G(3) 100,000 D $ 0 0 D

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

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 (Month/Day/Year)

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

Series B Common Stock

(1)

06/11/2025

C

100,000

(1)

(1)

Series A Common Stock

100,000

$ 0

74,773,276

D

Series B Common Stock

(1)

(1)

(1)

Series A Common Stock

11,945,830

11,945,830

I

By The Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023(4)

Series B Common Stock

(1)

(1)

(1)

Series A Common Stock

517,006

517,006

I

By The Elizabeth L. Bialecki Irrevocable GST Trust of 2023(5)

Series B Common Stock

(1)

(1)

(1)

Series A Common Stock

517,006

517,006

I

By The Andrew P. Bialecki Irrevocable GST Trust of 2023(6)

Series B Common Stock

(1)

(1)

(1)

Series A Common Stock

43,218

43,218

I

By spouse

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Bialecki Andrew C/O KLAVIYO, INC. 125 SUMMER STREET, 6TH FLOOR BOSTON, MA 02110	X	X	Chief Executive Officer

Signatures

/s/ Landon Edmond, Attorney-in-Fact		06/11/2025
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(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)	Each share of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.
(2)	The Reporting Person directed the transfer of 100,000 shares of their Series B Common Stock in connection with a bona fide gift to a donor-advised fund, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the transfer pursuant to the Issuer's certificate of incorporation.
(3)	Represents a bona fide gift of 100,000 shares of stock from the Reporting Person to a donor-advised fund. The Reporting Person directed the transfer of 100,000 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the transfer.
(4)	Shares held by the Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023, of which the Reporting Person serves as trustee. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose.
(5)	Shares held by the Elizabeth L. Bialecki Irrevocable GST Trust of 2023, of which the Reporting Person serves as a trustee. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose.
(6)	Shares held by the Andrew P. Bialecki Irrevocable GST Trust of 2023, of which the Reporting Person's spouse serves as a trustee. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose.

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