Klaviyo (KVYO) founder Andrew Bialecki reports 35.1% beneficial stake

Rhea-AI Filing Summary

Klaviyo, Inc. (KVYO) received an updated ownership report showing that co-founder Andrew Bialecki beneficially owns 78,163,529 shares of Series A common stock on an as-converted basis, representing 35.1% of the class as of December 31, 2025.

This stake includes shares underlying Series B common stock held directly by Bialecki, his spouse, and several 2023 family trusts for which he or his spouse serve as trustee. He is reported to have sole voting and dispositive power over all 78,163,529 shares and no shared voting or dispositive authority.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 3)

Klaviyo, Inc. (the "Issuer")

(Name of Issuer)

Series A common stock, par value $0.001 per share (the "Series A Common Stock")

(Title of Class of Securities)

49845K101

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 49845K101

1

Names of Reporting Persons

Bialecki Andrew

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 78,163,529.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 78,163,529.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

78,163,529.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

35.1 %

12

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Klaviyo, Inc. (the "Issuer")
(b)	Address of issuer's principal executive offices: 125 Summer Street, 6th Floor, Boston, MA, 02110
Item 2.
(a)	Name of person filing: This statement is filed on behalf of Andrew Bialecki (the "Reporting Person").
(b)	Address or principal business office or, if none, residence: The business address of the Reporting Person is c/o Klaviyo, Inc., 125 Summer Street, 6th Floor, Boston, MA 02110.
(c)	Citizenship: The Reporting Person is a citizen of the United States of America.
(d)	Title of class of securities: Series A common stock, par value $0.001 per share (the "Series A Common Stock")
(e)	CUSIP No.: 49845K101
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: The ownership information below represents beneficial ownership of Series A Common Stock of the Issuer as of December 31, 2025, based on (i) 144,262,443 shares of Series A Common Stock outstanding as of December 31, 2025, as reported by the Issuer to the Reporting Person, plus (ii) an aggregate of 78,163,529 shares of Series A Common Stock issuable upon conversion of shares of the Issuer's Series B common stock, par value $0.001 per share (the "Series B Common Stock"), beneficially owned by the Reporting Person, which are deemed outstanding pursuant to SEC Rule 13-3(d)(1)(i) only for purposes of computing the percentage ownership of the Reporting Person. The Reporting Person may be deemed to be the beneficial owner of 78,163,529 shares of Series A Common Stock, which includes: (i) 69,568,889 shares of Series A Common Stock underlying shares of Series B Common Stock held directly by the Reporting Person, (ii) 43,218 shares of Series A Common Stock underlying shares of Series B Common Stock held by the Reporting Person's spouse, (iii) 7,517,410 shares of Series A Common Stock underlying shares of Series B Common Stock held by the Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023, of which the Reporting Person serves as trustee, (iv) 517,006 shares of Series A Common Stock underlying shares of Series B Common Stock held by the Andrew P. Bialecki Irrevocable GST Trust of 2023, of which the Reporting Person's spouse serves as a trustee, and (v) 517,006 shares of Series A Common Stock underlying shares of Series B Common Stock held by the Elizabeth L. Bialecki Irrevocable GST Trust of 2023, of which the Reporting Person serves as a trustee.
(b)	Percent of class: 35.1%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 78,163,529
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 78,163,529
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.	Certifications:
	Not Applicable

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Bialecki Andrew

Signature:	/s/ Andrew Bialecki
Name/Title:	Andrew Bialecki
Date:	02/10/2026

FAQ

How many Klaviyo (KVYO) shares does Andrew Bialecki beneficially own?

Andrew Bialecki beneficially owns 78,163,529 shares of Klaviyo Series A common stock on an as-converted basis. This total includes shares underlying Series B stock held directly, by his spouse, and in several 2023 family trusts.

What percentage of Klaviyo (KVYO) Series A common stock does Andrew Bialecki hold?

Andrew Bialecki holds 35.1% of Klaviyo’s Series A common stock on an as-converted basis as of December 31, 2025. This percentage is calculated using the company’s reported outstanding shares plus his convertible Series B holdings.

How is Andrew Bialecki’s Klaviyo (KVYO) ownership structured?

His 78,163,529-share beneficial stake includes direct Series B holdings, shares held by his spouse, and shares held in three 2023 trusts. He or his spouse serve as trustee on these trusts, giving him beneficial ownership of the underlying Series A shares.

Does Andrew Bialecki share voting control over his Klaviyo (KVYO) shares?

No. The filing states he has sole voting power and sole dispositive power over 78,163,529 shares, with zero shared voting or shared dispositive power. This indicates centralized control over voting and disposition decisions for these shares.

What share count did Klaviyo (KVYO) report for calculating Andrew Bialecki’s ownership?

Klaviyo reported 144,262,443 shares of Series A common stock outstanding as of December 31, 2025. The ownership percentage adds Bialecki’s 78,163,529 as-converted Series A shares to this figure solely for computing his beneficial ownership under SEC rules.

Which entities related to Andrew Bialecki hold Klaviyo (KVYO) shares?

Related holdings include the Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023, the Andrew P. Bialecki Irrevocable GST Trust of 2023, and the Elizabeth L. Bialecki Irrevocable GST Trust of 2023, along with shares held by his spouse.