September 18, 2019

Dennis P. Calvert
Chief Executive Officer
BioLargo, Inc.
14921 Chestnut Street
Westminster, CA 92683

       Re: BioLargo, Inc.
           Post-Effective Amendment to Form S-1
           Filed August 30, 2019
           File No. 333-220482

Dear Mr. Calvert:

       We have reviewed your post-effective amendment and have the following
comment.

       Please respond to this letter by amending your registration statement
and providing the
requested information. If you do not believe our comment applies 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 this comment, we may have additional comments.

Post-Effective Amendment to Form S-1 filed August 30, 2019

General

1.     This post-effective amendment was filed to update the financial
information in your Form
       S-1, which last contained audited financial statements for the fiscal
year ended December
       31, 2017. Under Section 10(a)(3) of the Securities Act, "when a
prospectus is used more
       than nine months after the effective date of the registration statement,
the [audited
       financial] information contained therein shall be as of a date not more
than sixteen months
       prior to such use." Please tell us whether you engaged in the offer or
sale of your
       securities using the prospectus from April 30, 2019 and the present,
during which time the
       audited financial statements in the prospectus were not current.
 Dennis P. Calvert
FirstName Inc.
BioLargo, LastNameDennis P. Calvert
Comapany 18, 2019
September NameBioLargo, Inc.
Page 2
September 18, 2019 Page 2
FirstName LastName
        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.

      Please contact Sergio Chinos, Staff Attorney, at (202) 551-7844 or Jay
Ingram, Legal
Branch Chief, at (202) 551-3397 with any other questions.



                                                          Sincerely,

                                                          Division of
Corporation Finance
                                                          Office of
Manufacturing and
                                                          Construction
cc:      Christopher A. Wilson