Klaviyo (KVYO) Co-CEO Bialecki sells 212,529 shares under 10b5-1 plan

Rhea-AI Filing Summary

Klaviyo, Inc. Co-CEO Andrew Bialecki reported an insider transaction involving a derivative conversion and share sale. On May 26, 2026, he converted 212,529 shares linked to Series B Common Stock into 212,529 shares of Series A Common Stock, then sold 212,529 Series A shares at a weighted average price of $14.61 per share in an open-market transaction.

Following the sale, he continued to hold 66,731,589 shares of Series B Common Stock directly and additional Series B shares indirectly through family trusts and his spouse. The filing states these transactions were carried out under a Rule 10b5-1 trading plan adopted on May 20, 2025, indicating they were pre-scheduled.

Insights

Equity compensation and insider-trading analyst

Pre-planned conversion and sale; large position remains.

The filing shows an exercise-and-sell pattern. Andrew Bialecki converted 212,529 shares tied to Series B Common Stock into Series A Common Stock, then sold 212,529 Series A shares at a weighted average of $14.61 per share in an open-market transaction.

The derivative record indicates 66,731,589 Series B shares held directly after the transaction, plus significant indirect holdings through trusts and his spouse. This suggests the sale represents a small portion of his overall economic exposure visible in this filing.

The footnotes confirm these trades were executed under a Rule 10b5-1 trading plan adopted on May 20, 2025, meaning they were pre-arranged rather than discretionary. Subsequent company filings may provide further context on any future transactions under this plan.

Insider Trade Summary 10b5-1

Net Seller: 212,529 shares ($3,105,049)

Net Sell 7 txns

Insider Bialecki Andrew

Role Co-Chief Executive Officer

Sold 212,529 shs ($3.11M)

Type	Security	Shares	Price	Value
Conversion	Series B Common Stock	212,529	$0.00	--
Conversion	Series A Common Stock	212,529	$0.00	--
Sale	Series A Common Stock	212,529	$14.61	$3.11M
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 — 66,731,589 shares (Direct, null); Series A Common Stock — 212,529 shares (Direct, null); 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 $14.43 to $15.00 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.

Key Figures

Shares sold: 212,529 shares Weighted average sale price: $14.61 per share Direct Series B holdings after transaction: 66,731,589 shares +4 more

7 metrics

Shares sold 212,529 shares Series A Common Stock sold in open market on May 26, 2026

Weighted average sale price $14.61 per share Series A Common Stock sale range $14.43–$15.00

Direct Series B holdings after transaction 66,731,589 shares Series B Common Stock held directly following conversion entry

Grantor Retained Annuity Trust holdings 7,517,410 shares Series B Common Stock held by Grantor Retained Annuity Trust I of 2023

Irrevocable GST Trust holdings (Andrew trust) 517,006 shares Series B Common Stock held by Andrew P. Bialecki Irrevocable GST Trust of 2023

Irrevocable GST Trust holdings (Elizabeth trust) 517,006 shares Series B Common Stock held by Elizabeth L. Bialecki Irrevocable GST Trust of 2023

Spouse-held shares 43,218 shares Series B Common Stock held indirectly by spouse

Key Terms

Rule 10b5-1 trading plan, Series B Common Stock, Series A Common Stock, Grantor Retained Annuity Trust, +1 more

5 terms

Rule 10b5-1 trading plan regulatory

"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."

A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.

Series B Common Stock financial

"Each share of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible..."

Series A Common Stock financial

"…into one share of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock")…"

Series A common stock is a specific class of a company’s ordinary shares issued during an early formal funding round, carrying the ownership rights and voting power tied to that class. For investors it signals an early-stage equity claim with potential upside if the business grows, but also greater risk and typically less liquidity than shares in mature, publicly traded firms—imagine buying a seat on a startup’s team before the company has proven itself.

Grantor Retained Annuity Trust financial

"Shares held by the Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023, of which the Reporting Person serves as trustee."

A grantor retained annuity trust (GRAT) is an estate-planning tool where the person who creates the trust transfers assets into it but receives fixed cash payments (an annuity) from the trust for a set number of years; whatever remains after that term passes to designated beneficiaries. It matters to investors because it can shift future appreciation of assets out of the creator’s taxable estate—like putting an asset into a timed vending machine that pays you fixed amounts while any extra value that grows inside the machine goes to heirs with reduced gift or estate tax consequences.

Section 16 beneficial ownership regulatory

"The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein..."

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 MASSACHUSETTS 02110

(City) (State) (Zip)

UNITED STATES

(Country)

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)
	Co-Chief Executive Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/26/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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	05/26/2026		C(1)		212,529	A	(2)	212,529	D
Series A Common Stock	05/26/2026		S(1)		212,529	D	$14.61(3)	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)	05/26/2026		C(1)			212,529	(2)	(2)	Series A Common Stock	212,529	$0	66,731,589	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 $14.43 to $15.00 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	05/28/2026
	** 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.
* Form 4: SEC 1474 (03-26)

FAQ

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

Andrew Bialecki reported converting 212,529 shares into Series A Common Stock and selling 212,529 Series A shares. The sale was an open-market transaction at a weighted average price of $14.61 per share, according to the Form 4 filing details.

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

He sold 212,529 shares of Klaviyo’s Series A Common Stock. The weighted average sale price was $14.61 per share, with individual trades executed between $14.43 and $15.00 per share, as described in the Form 4 transaction footnote.

Were Andrew Bialecki’s Klaviyo (KVYO) share sales under a Rule 10b5-1 plan?

Yes. The filing states the transactions were effected under a Rule 10b5-1 trading plan adopted on May 20, 2025. Such plans pre-schedule trades, indicating the timing of these sales was determined in advance rather than made opportunistically.

What Klaviyo (KVYO) holdings does Andrew Bialecki have after this Form 4 transaction?

After the reported transactions, he held 66,731,589 shares of Series B Common Stock directly. The filing also lists additional indirect Series B holdings through the Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023 and two irrevocable GST trusts, plus shares held by his spouse.

How are Andrew Bialecki’s trust-held Klaviyo (KVYO) shares treated in the Form 4?

Shares held by several 2023 trusts are reported as indirect holdings. The footnotes state he disclaims Section 16 beneficial ownership of those shares except for any pecuniary interest, clarifying they are legally owned by the respective trusts, not directly by him.

What is the relationship between Klaviyo Series A and Series B Common Stock in this filing?

Each share of Series B Common Stock is convertible into one share of Series A Common Stock. The footnote explains Series B can be converted at any time at the holder’s option and will automatically convert into Series A upon certain events, with no expiration date for Series B.