Mailstop 3561

                                                            September 13, 2018

Via E-mail
Helmy Eltoukhy
Chief Executive Officer
Guardant Health, Inc.
505 Penobscot Dr.
Redwood City, California 94063

       Re:      Guardant Health, Inc.
                Registration Statement on Form S-1
                Filed September 6, 2018
                File No. 333-227206

Dear Mr. Eltoukhy:

       We have reviewed your registration statement and have the following
comments. In
some of our comments, we may ask you to provide us with information so we may
better
understand your disclosure.

       Please respond to this letter by amending your registration statement
and providing the
requested information. If you do not believe our comments apply to your facts
and
circumstances or do not believe an amendment is appropriate, please tell us why
in your
response.

       After reviewing any amendment to your registration statement and the
information you
provide in response to these comments, we may have additional comments.

Use of Proceeds, page 59

1.     Please specify the principal purposes of the net proceeds that you will
receive from the
       offering, including the approximate amount intended to be used for each
such purpose.
       See Item 504 of Regulation S-K.

Dilution, page 63

2.     Please tell us and disclose your basis for not deducting redeemable
non-controlling
       interest amounts in arriving at the historical and pro forma net
tangible book value
       amounts presented. Alternatively, revise your computations accordingly.
 Helmy Eltoukhy
Guardant Health, Inc.
September 13, 2018
Page 2


Management's Discussion and Analysis of Financial Condition and Results of
Operations
Comparison of the six months ended June 30, 2017 and 2018, page 74

3.      We note your disclosure that cash receipts relative to the number of
tests processed in
        period were higher in the six months ended June 30, 2018 compared to
the prior period.
        Please disclose the period-to-period change. See Item 303(b)(2) of
Regulation S-K.

        We remind you that the company and its management are responsible for
the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action
or absence of
action by the staff.

       Refer to Rules 460 and 461 regarding requests for acceleration. Please
allow adequate
time for us to review any amendment prior to the requested effective date of
the registration
statement.

       You may contact Linda Cvrkel at (202) 551-3813 or Rufus Decker at (202)
551-3769 if
you have questions regarding comments on the financial statements and related
matters. Please
contact Michael Killoy at (202) 551-7576 or Brigitte Lippmann at (202) 551-3356
with any other
questions.


                                                            Sincerely,

                                                            /s/ Brigitte
Lippmann (for)

                                                            John Reynolds
                                                            Assistant Director
                                                            Office of
Beverages, Apparel,
                                                            and Mining

cc:     B. Shayne Kennedy
        Latham & Watkins LLP