Klaviyo, Inc. (KVYO) CEO files insider stock sale and conversion report

Rhea-AI Filing Summary

Klaviyo, Inc. Chief Executive Officer, director and 10% owner Andrew P. Bialecki reported stock transactions in Klaviyo carried out under a Rule 10b5-1 trading plan adopted on May 20, 2025. On December 16, 2025, he converted 138,648 shares of Series B Common Stock into Series A Common Stock and sold 138,648 Series A shares at a weighted average price of $29.04 per share, with sale prices ranging from $28.58 to $29.42. On December 17, 2025, he converted 100,000 Series B shares and sold 100,000 Series A shares at a weighted average price of $30.4 per share, in transactions between $30.00 and $30.71. After these trades, Bialecki directly held 69,668,889 shares of Series B Common Stock and reported additional indirect interests, including 7,517,410 Series A shares held by the Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023, for which he disclaims beneficial ownership except to the extent of any pecuniary interest.

Insider Trade Summary

Net Seller: 238,648 shares ($7,066,338)

Net Sell 10 txns

Insider Bialecki Andrew

Role Chief Executive Officer

Sold 238,648 shs ($7.07M)

Type	Security	Shares	Price	Value
Conversion	Series B Common Stock	100,000	$0.00	--
Conversion	Series A Common Stock	100,000	$0.00	--
Sale	Series A Common Stock	100,000	$30.40	$3.04M
Conversion	Series B Common Stock	138,648	$0.00	--
Conversion	Series A Common Stock	138,648	$0.00	--
Sale	Series A Common Stock	138,648	$29.04	$4.03M
holding	Series B Common Stock	--	--	--
holding	Series B Common Stock	--	--	--
holding	Series B Common Stock	--	--	--
holding	Series B Common Stock	--	--	--

Holdings After Transaction: Series B Common Stock — 69,668,889 shares (Direct); Series A Common Stock — 100,000 shares (Direct); Series B Common Stock — 7,517,410 shares (Indirect, By The Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023)

Footnotes (1)

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. 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. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $28.58 to $29.42 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. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $30.00 to $30.71 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. 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. 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. 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.

Form 4 Insider Transactions: What Each Field Means →

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

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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)
12/16/2025

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	12/16/2025		C(1)		138,648	A	(2)	138,648	D
Series A Common Stock	12/16/2025		S(1)		138,648	D	$29.04(3)	0	D
Series A Common Stock	12/17/2025		C(1)		100,000	A	(2)	100,000	D
Series A Common Stock	12/17/2025		S(1)		100,000	D	$30.4(4)	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)	12/16/2025		C(1)			138,648	(2)	(2)	Series A Common Stock	138,648	$0	69,768,889	D
Series B Common Stock	(2)	12/17/2025		C(1)			100,000	(2)	(2)	Series A Common Stock	100,000	$0	69,668,889	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(5)
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(6)
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(7)
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 $28.58 to $29.42 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. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $30.00 to $30.71 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.

5. 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.

6. 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.

7. 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	12/17/2025
	** 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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider transactions did Klaviyo (KVYO) report for Andrew P. Bialecki on December 16–17, 2025?

On December 16, 2025, Andrew P. Bialecki converted 138,648 Series B Common shares into Series A Common Stock and sold 138,648 Series A shares. On December 17, 2025, he converted 100,000 Series B shares and sold 100,000 Series A shares.

At what prices did Andrew P. Bialecki sell Klaviyo (KVYO) Series A Common Stock?

On December 16, 2025, he sold 138,648 Series A shares at a weighted average price of $29.04 per share, with prices from $28.58 to $29.42. On December 17, 2025, he sold 100,000 Series A shares at a weighted average price of $30.4, in a range of $30.00 to $30.71.

What is the relationship between Klaviyo (KVYO) Series A and Series B Common Stock?

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

What trading plan governed the reported Klaviyo (KVYO) stock transactions?

The reported transactions were effected by the reporting person pursuant to a Rule 10b5-1 trading plan adopted on May 20, 2025.

How many Klaviyo (KVYO) Series B shares does Andrew P. Bialecki hold directly after these transactions?

Following the reported conversions and sales, Andrew P. Bialecki directly held 69,668,889 shares of Klaviyo’s Series B Common Stock.

What indirect Klaviyo (KVYO) holdings are reported for Andrew P. Bialecki?

Indirect interests reported include 7,517,410 Series A shares held by the Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023, 517,006 Series A shares held by the Elizabeth L. Bialecki Irrevocable GST Trust of 2023, 517,006 Series A shares held by the Andrew P. Bialecki Irrevocable GST Trust of 2023, and 43,218 Series A shares held by his spouse. The reporting person disclaims Section 16 beneficial ownership of these shares except to the extent of any pecuniary interest.