Klaviyo insider Andrew Bialecki disposes of 137,224 shares at $27.68–$31.77

Rhea-AI Filing Summary

Andrew Bialecki, Klaviyo CEO and director, reported insider transactions on 09/30/2025 under a Rule 10b5-1 plan adopted 05/20/2025. He received 137,224 shares of Series B common stock that are convertible into 137,224 shares of Series A common stock, and sold the full position in multiple block sales on the same date. The sales occurred at weighted-average prices disclosed in ranges from $27.68 to $31.77, with individual weighted-average sale prices reported as $31.24, $30.28, $29.03, $28.22, and $27.70. After these transactions the reporting person’s direct beneficial ownership of Series A common stock is 0. The Form 4 lists additional indirect holdings by trusts for which the reporting person is trustee, with specific trust-held share amounts disclosed.

Positive

• Transactions disclosed under a Rule 10b5-1 plan, indicating preplanned, automated trading
• Full transaction details provided including price ranges and weighted-average prices for each tranche

Negative

• Reporting Person's direct beneficial ownership reduced to 0 for the reported Series A shares
• No aggregate proceeds disclosed in the filing, requiring requests for full breakdowns if needed

Insights

Corporate Governance Expert

CEO sold entire 137,224-share stake under a preplanned 10b5-1 program.

The Form 4 shows the Reporting Person adopted a Rule 10b5-1 trading plan on 05/20/2025 and executed purchases and multiple sales on 09/30/2025, resulting in no direct Series A shares held thereafter.

This is a routine, disclosed insider liquidity event rather than an unexplained, unscheduled sale; the filing also documents trust-held indirect positions where the reporting person disclaims beneficial ownership except to the extent of any pecuniary interest.

Equity Markets Analyst

Sales totaled 137,224 shares across price ranges of $27.68–$31.77, indicating execution over multiple blocks.

The Form 4 reports weighted-average prices and price ranges for each tranche, which investors can use to approximate realized proceeds but the filing does not disclose aggregate proceeds.

Because all reported direct Series A holdings were sold, short-term insider ownership tied to these specific shares is fully liquidated; indirect trust holdings remain as disclosed on the form.

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).

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)
09/30/2025

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	09/30/2025		C(1)		137,224	A	(2)	137,224	D
Series A Common Stock	09/30/2025		S(1)		17,960	D	$31.24(3)	119,264	D
Series A Common Stock	09/30/2025		S(1)		6,048	D	$30.28(4)	113,216	D
Series A Common Stock	09/30/2025		S(1)		44,672	D	$29.03(5)	68,544	D
Series A Common Stock	09/30/2025		S(1)		39,733	D	$28.22(6)	28,811	D
Series A Common Stock	09/30/2025		S(1)		28,811	D	$27.7(7)	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)	09/30/2025		C(1)			137,224	(2)	(2)	Series A Common Stock	137,224	$0	74,456,245	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(8)
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(9)
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(10)
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 $30.82 to $31.77 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 $29.80 to $30.76 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. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $28.77 to $29.76 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.

6. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $27.77 to $28.76 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.

7. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $27.68 to $27.75 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.

8. 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.

9. 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.

10. 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	10/02/2025
	** 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.
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FAQ

What did Klaviyo CEO Andrew Bialecki report on Form 4 (KVYO)?

The Form 4 reports acquisitions and multiple sales on 09/30/2025 under a Rule 10b5-1 plan, starting with 137,224 Series B shares convertible into Series A and ending with 0 direct Series A shares.

How many shares did the CEO sell and at what prices?

The filing shows sales totaling 137,224 shares in tranches with weighted-average prices reported and ranges from $27.68 to $31.77.

When was the Rule 10b5-1 trading plan adopted?

The Form 4 states the trading plan was adopted on 05/20/2025.

Does the Form 4 show any remaining indirect holdings?

Yes, the filing discloses indirect holdings held by trusts, including specific share amounts for the Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023 and two irrevocable GST trusts.

Are total proceeds from the sales disclosed on the Form 4?

No. The filing provides weighted-average prices and ranges for each tranche but does not state aggregate proceeds; the reporting person offers to provide detailed breakdowns upon request.