[Form 4] Klaviyo, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Andrew Bialecki, Klaviyo CEO, reported transactions under a Rule 10b5-1 trading plan executed on 10/07/2025. The report shows a conversion of 159,508 shares of Series B into Series A common stock followed by sales of those shares in multiple transactions at weighted average prices in the <$25.07–$25.32> range. After the reported sales, the filing indicates 0 direct shares beneficially owned by the reporting person.

The filing lists additional indirect holdings via trusts and spouse-controlled accounts totaling 8,594,640 Series A-equivalent shares across several trust and spouse relationships, with explicit disclaimers about Section 16 beneficial ownership limits. The transactions were effected pursuant to a 10b5-1 plan adopted on 5/20/2025.

Positive

• Transactions executed under a documented 10b5-1 trading plan, indicating pre-planned execution
• Conversion of 159,508 Series B shares into Series A shares was completed as disclosed
• Material indirect holdings retained through trusts and spouse accounts (millions of shares)

Negative

• Direct beneficial ownership reduced to 0 following conversion and sales of 159,508 shares
• Sales executed at prices ranging from $24.95 to $26.13, indicating significant insider liquidity

Insights

Corporate Governance Expert

Insider used a pre-established 10b5-1 plan to convert and fully sell direct holdings.

The reporting person executed a plan adopted on 5/20/2025 to convert 159,508 Series B shares into Series A and then sell those shares across multiple trades at weighted average prices near $25 per share. Using a documented trading plan helps demonstrate an affirmative defense under Rule 10b5-1.

The filing also shows substantial indirect holdings through trusts and spouse accounts (totaling millions of shares), which remain in place; monitor formal disclosures if trust ownership or trustee roles change in upcoming filings within the next year.

Equity Markets Expert

Net effect: direct beneficial ownership reduced to zero while indirect holdings remain substantial.

The conversion plus sales removed 159,508 directly held shares from the reporting person's direct ownership, with sales executed across price ranges of $24.95 to $26.13 per share as disclosed. Large insider sales executed under a 10b5-1 plan can increase available float and may be noticed by market participants.

Watch for any further Form 4 filings or amendments within 30–90 days that disclose additional sales, plan terminations, or changes to indirect holdings; price ranges provided allow calculation of gross proceeds if needed.

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)
10/07/2025

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	10/07/2025		C(1)		159,508	A	(2)	159,508	D
Series A Common Stock	10/07/2025		S(1)		144,890	D	$25.32(3)	14,618	D
Series A Common Stock	10/07/2025		S(1)		14,618	D	$25.07(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)	10/07/2025		C(1)			159,508	(2)	(2)	Series A Common Stock	159,508	$0	74,296,737	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 $25.135 to $26.13 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 $24.95 to $25.13 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	10/09/2025
	** 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 did Klaviyo CEO Andrew Bialecki report on Form 4 (KVYO)?

The report discloses conversion of 159,508 Series B shares into Series A and subsequent sales of those 159,508 shares under a Rule 10b5-1 plan adopted on 5/20/2025.

How many shares did the reporting person sell and at what prices?

The filing shows sales totaling 159,508 shares in multiple transactions with weighted average prices reported and ranges disclosed from $24.95 to $26.13 per share.

Does Andrew Bialecki still hold Klaviyo shares after these transactions?

Direct beneficial ownership is reported as 0 shares following the transactions, but the filing shows substantial indirect holdings via trusts and spouse accounts totaling multiple millions of Series A-equivalent shares.

Were these trades discretionary or part of a plan?

The trades were effected pursuant to a Rule 10b5-1 trading plan adopted on 5/20/2025, as stated in the filing.

Who signed the Form 4 and when was it filed?

The Form 4 is signed by an attorney-in-fact, Landon Edmond, with the signature date shown as 10/09/2025.