Klaviyo (KVYO) CEO Andrew Bialecki Logs Planned Series A Stock Sales

Rhea-AI Filing Summary

Klaviyo, Inc. Chief Executive Officer, director and 10% owner Andrew P. Bialecki reported planned share sales under a Rule 10b5-1 trading plan. On 12/02/2025, he converted 142,045 shares of Series B Common Stock into Series A Common Stock and sold the same number of Series A shares at a weighted average price of $28.62 per share. On 12/04/2025, he similarly converted and sold 952 Series A shares at $30 per share. Each Series B share is convertible into one Series A share and has no expiration. Following these transactions, he continued to beneficially own 73,557,899 Series B shares directly, along with additional Series A interests held indirectly through several 2023 family trusts and by his spouse.

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

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

X

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Bialecki Andrew

(Last) (First) (Middle)

C/O KLAVIYO, INC.

125 SUMMER STREET, 6TH FLOOR

(Street)

BOSTON MA 02110

(City) (State) (Zip)

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

3. Date of Earliest Transaction (Month/Day/Year)
12/02/2025

4. If Amendment, Date of 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

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	12/02/2025		C(1)		142,045	A	(2)	142,045	D
Series A Common Stock	12/02/2025		S(1)		142,045	D	$28.62(3)	0	D
Series A Common Stock	12/04/2025		C(1)		952	A	(2)	952	D
Series A Common Stock	12/04/2025		S(1)		952	D	$30	0	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 (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 Securities Underlying Derivative Security (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: 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	(2)	12/02/2025		C(1)			142,045	(2)	(2)	Series A Common Stock	142,045	$0	73,558,851	D
Series B Common Stock	(2)	12/04/2025		C(1)			952	(2)	(2)	Series A Common Stock	952	$0	73,557,899	D
Series B Common Stock	(2)							(2)	(2)	Series A Common Stock	7,517,410		7,517,410	I	By The Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023(4)
Series B Common Stock	(2)							(2)	(2)	Series A Common Stock	517,006		517,006	I	By The Elizabeth L. Bialecki Irrevocable GST Trust of 2023(5)
Series B Common Stock	(2)							(2)	(2)	Series A Common Stock	517,006		517,006	I	By The Andrew P. Bialecki Irrevocable GST Trust of 2023(6)
Series B Common Stock	(2)							(2)	(2)	Series A Common Stock	43,218		43,218	I	By spouse

Explanation of Responses:

1. These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025.

2. 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.

3. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $28.20 to $28.87 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

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.

Remarks:

	/s/ Landon Edmond, Attorney-in-Fact	12/04/2025
	** Signature of Reporting Person	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).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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FAQ

What insider transaction did Klaviyo (KVYO) CEO Andrew Bialecki report?

Andrew P. Bialecki reported converting Series B Common Stock into Series A Common Stock and selling those Series A shares in open-market transactions on 12/02/2025 and 12/04/2025.

How many Klaviyo (KVYO) shares did Andrew Bialecki sell and at what prices?

He sold 142,045 Series A shares on 12/02/2025 at a weighted average price of $28.62 per share and 952 Series A shares on 12/04/2025 at $30 per share.

Was the Klaviyo (KVYO) CEO’s trade done under a Rule 10b5-1 plan?

Yes. The filing states the transactions were effected pursuant to a Rule 10b5-1 trading plan adopted by Andrew P. Bialecki on May 20, 2025.

What is the difference between Klaviyo’s Series A and Series B Common Stock in this filing?

Each share of Series B Common Stock is convertible at any time at the holder’s option into one share of Series A Common Stock and will automatically convert into one Series A share upon certain events. The Series B stock has no expiration date.

How many Klaviyo (KVYO) shares does Andrew Bialecki still hold after these transactions?

After the reported transactions, he held 73,557,899 shares of Series B Common Stock directly as a derivative security, plus additional Series A Common Stock held indirectly through several 2023 family trusts and by his spouse.

What indirect holdings of Klaviyo (KVYO) stock are reported for Andrew Bialecki?

The filing lists indirect holdings of 7,517,410, 517,006, 517,006, and 43,218 shares of Series A Common Stock through the Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023, the Elizabeth L. Bialecki Irrevocable GST Trust of 2023, the Andrew P. Bialecki Irrevocable GST Trust of 2023, and by his spouse, respectively.

Does Andrew Bialecki claim full beneficial ownership of shares held in the Klaviyo-related trusts?

No. For each listed trust, he disclaims Section 16 beneficial ownership of those shares except to the extent of his pecuniary interest, and states the report should not be deemed an admission of beneficial ownership.