Item 1.01

Entry into a Material Definitive Agreement.

Open Market Sale Agreement

On August 23, 2024, Guardant Health, Inc. (the "Company") entered into an Open Market Sale Agreement^SM (the "Sales Agreement") with Jefferies LLC (the "Agent") with respect to an at-the-market offering programunder which the Company may offer and sell, from time to time at its sole discretion, shares of the Company's common stock, par value $0.00001 per share (the "Common Stock"), having aggregate gross proceeds of up to $400.0 million (the "Shares") through the Agent, acting as sales agent.

Any Shares to be offered and sold under the Sales Agreement will be issued and sold pursuant to the Company's shelf registration statement on Form S-3, whichwas filed with the U.S. Securities and Exchange Commission (the "SEC") on May 22, 2023 and became effective immediately upon filing (File No. 333-272121).The Company filed a prospectus supplement with the SEC on August 23, 2024 in connection with the offer and sale of the Shares pursuant to the Sales Agreement, which supplements the base prospectus included in the Registration Statement.

The Company will designate the maximum amount of Shares to be sold through the Agent in any placement under the Sales Agreement. Subject to the terms and conditions of the Sales Agreement, the Agent has agreed to use its commercially reasonable efforts to sell on the Company's behalf all of the Shares requested to be sold by the Company. Upon delivery of a placement notice and subject to the terms and conditions of the Sales Agreement, the Agent may sell the Shares by methods deemed to be an "at the market offering" as defined in Rule 415(a)(4) promulgated under the Securities Act of 1933, as amended (the "Securities Act"). The Company may instruct the Agent not to sell Shares if the sales cannot be effected at or above a price designated by the Company in a placement notice. The Company or the Agent may suspend the offering of Shares upon proper notice to the other party. The Company and the Agent each have the right, by giving written notice as specified in the Sales Agreement, to terminate the Sales Agreement in each party's sole discretion at any time.

The Sales Agreement provides that the Agent will be entitled to aggregate compensation for its services of up to 3.0% of the gross sales price per share of all Shares sold through the Agent under the Sales Agreement. The Company has no obligation to sell any Shares under the Sales Agreement. The Company has agreed in the Sales Agreement to provide indemnification and contribution to the Agent against certain liabilities, including liabilities under the Securities Act.

The foregoing description of the Sales Agreement is not complete and is qualified in its entirety by reference to the full text of such agreement, a copy of which is filed as Exhibit 1.1 to this Current Report on Form 8-K(the "Current Report") and is incorporated herein by reference.

The legal opinion of Gunderson Dettmer Stough Villeneuve Franklin & Hachigian, LLP relating to the validity of the Shares is filed as Exhibit 5.1 to this Current Report.

This Current Report shall not constitute an offer to sell or the solicitation of an offer to buy any Shares, nor shall there be any offer, solicitation or sale of the Shares in any state or country in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or country.

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