Results of Operations and Financial Condition On August 5, 2026, Klaviyo, Inc. (the "Company") issued a press release announcing financial results for the second quarter ended June 30, 2026. A copy of the release is furnished with this report as Exhibit 99.1. The information in this Current Report on Form 8-K, including Exhibit 99.1 attached hereto, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “E…

Chief Financial Officer and principal financial and accounting officer — Erica Smith: Klaviyo appointed Erica Smith as the Chief Financial Officer, a significant leadership addition.

Results of Operations and Financial Condition On May 5, 2026, Klaviyo, Inc. (the "Company") issued a press release announcing financial results for the first quarter ended March 31, 2026. A copy of the release is furnished with this report as Exhibit 99.1.

Chief Financial Officer — Amanda Whalen: Ms. Whalen informed the Company of her intention to step down from her role as Chief Financial Officer.

Other Events On March 2, 2026, Klaviyo, Inc. (the “Company”) announced that its board of directors authorized a share repurchase program (the “Share Repurchase Program”), pursuant to which the Company may repurchase up to $500 million in the aggregate of the Company’s issued and outstanding shares of Series A Common Stock. Repurchases under the Share Repurchase Program may be made from time to time in the open market, through privately negotiated transactions or other means, including pursuan…

Results of Operations and Financial Condition On February 10, 2026, Klaviyo, Inc. (“Klaviyo” or the “Company”) issued a press release announcing financial results for the quarter and fiscal year ended December 31, 2025. A copy of the release is furnished with this report as Exhibit 99.1. The information in this Current Report on Form 8-K, including Exhibit 99.1 attached hereto, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Ac…

co-Chief Executive Officer — Chano Fernández: Chano Fernández was appointed as co-Chief Executive Officer, expanding the leadership structure.

Results of Operations and Financial Condition On November 5, 2025, Klaviyo, Inc. issued a press release announcing financial results for the third quarter ended September 30, 2025. A copy of the release is furnished with this report as Exhibit 99.1. The information in this Current Report on Form 8-K, including Exhibit 99.1 attached hereto, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Ac…

Interim Executive Officer — Chano Fernández: Chano Fernández was appointed as Interim Executive Officer and will no longer serve as Chairperson or on the Compensation Committee.

Entry into a Material Definitive Agreement. On August 13, 2025, Klaviyo, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Barclays Capital Inc., as underwriter (the “Underwriter”), and the selling stockholders named therein (the “Selling Stockholders”). Pursuant to the terms of the Underwriting Agreement, the Selling Stockholders sold an aggregate of 6,500,000 shares (the “Shares”) of the Company’s Series A common stock, par value $0.001 per shar…

President — Steve Rowland: Steve Rowland is retiring from his position as President with an orderly transition plan.

Results of Operations and Financial Condition On August 5, 2025, Klaviyo, Inc. issued a press release announcing financial results for the second quarter ended June 30, 2025. A copy of the release is furnished with this report as Exhibit 99.1. The information in this Current Report on Form 8-K, including Exhibit 99.1 attached hereto, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), o…

Entry into a Material Definitive Agreement. On May 14, 2025, Klaviyo, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Goldman Sachs & Co. LLC and Morgan Stanley & Co. LLC, as representatives of the several underwriters (the “Underwriters”), and the selling stockholder, Andrew Bialecki, the Company’s Chief Executive Officer and co-founder. Pursuant to the terms of the Underwriting Agreement, Mr. Bialecki sold an aggregate of 10,969,078 shares (th…

Results of Operations and Financial Condition On May 6, 2025, Klaviyo, Inc. issued a press release announcing financial results for the first quarter ended March 31, 2025. A copy of the release is furnished with this report as Exhibit 99.1. The information in this Current Report on Form 8-K, including Exhibit 99.1 attached hereto, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or o…

Results of Operations and Financial Condition On February 19, 2025, Klaviyo, Inc. (“Klaviyo” or the “Company”) issued a press release announcing financial results for the quarter and fiscal year ended December 31, 2024. A copy of the release is furnished with this report as Exhibit 99.1. The information in this Current Report on Form 8-K, including Exhibit 99.1 attached hereto, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Ac…

Results of Operations and Financial Condition On November 6, 2024, Klaviyo, Inc. issued a press release announcing financial results for the third quarter ended September 30, 2024. A copy of the release is furnished with this report as Exhibit 99.1. The information in this Current Report on Form 8-K, including Exhibit 99.1 attached hereto, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Ac…

Results of Operations and Financial Condition On August 7, 2024, Klaviyo, Inc. issued a press release announcing financial results for the second quarter ended June 30, 2024. A copy of the release is furnished with this report as Exhibit 99.1. The information in this Current Report on Form 8-K, including Exhibit 99.1 attached hereto, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), o…

Results of Operations and Financial Condition On May 8, 2024, Klaviyo, Inc. issued a press release announcing financial results for the first quarter ended March 31, 2024. A copy of the release is furnished with this report as Exhibit 99.1. The information in this Current Report on Form 8-K, including Exhibit 99.1 attached hereto, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or o…

Results of Operations and Financial Condition On February 27, 2024, Klaviyo, Inc. (“Klaviyo” or the “Company”) issued a press release announcing financial results for the quarter and fiscal year ended December 31, 2023. A copy of the release is furnished with this report as Exhibit 99.1. The information in this Current Report on Form 8-K, including Exhibit 99.1 attached hereto, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Ac…

Results of Operations and Financial Condition On November 7, 2023, Klaviyo, Inc. issued a press release announcing financial results for the third quarter ended September 30, 2023. A copy of the release is furnished with this report as Exhibit 99.1. The information in this Current Report on Form 8-K, including Exhibit 99.1 attached hereto, is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Ac…