September 28, 2018

Jonathan P. Mow
Chief Executive Officer
PhaseBio Pharmaceuticals, Inc.
Regus Del Mar
12707 High Bluff Drive, Suite 200
San Diego, CA 92130

       Re: PhaseBio Pharmaceuticals, Inc.
           Registration Statement on Form S-1
           Filed September 21, 2018
           File No. 333-227474

Dear Mr. Mow:

       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.

Registration Statement on Form S-1 filed September 21, 2018

Business
PB1046 for the Treatment of Pulmonary Arterial Hypertension, page 88

1.     We note your disclosure that you received a $2.8 million grant from the
National Institutes
       of Health to support the development of PB1046 for the treatment of PAH
in February
       2018. Please expand your disclosure to provide the material terms of the
grant, including
       any conditions on funding, obligations under the grant and the
intellectual property rights
 Jonathan P. Mow
PhaseBio Pharmaceuticals, Inc.
September 28, 2018
Page 2
       of each party. Please file as an exhibit any written agreements between
the company
       and NIH pursuant to Item 601(b)(10) of Regulation S-K, or tell us why
you do not believe
       this is required.
Index to Financial Statements
Notes to Financial Statements
2. Basis of Presentation and Significant Accounting Policies , page F-7

2.     On page 88, you disclose your receipt of a $2.8 million grant from the
National Institutes
       of Health in February 2018. Please disclose your accounting policy for
recognizing and
       classifying grants received as well as the nature and amount of this
grant, including any
       restrictions.
        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 Tabatha Mccullom at 202-551-3658 or Jim Rosenberg at
202-551-
3679 if you have questions regarding comments on the financial statements and
related matters.
Please contact Irene Paik at 202-551-6553 or Mary Beth Breslin at 202-551-3625
with any other
questions.



                                                            Sincerely,
FirstName LastNameJonathan P. Mow
                                                            Division of
Corporation Finance
Comapany NamePhaseBio Pharmaceuticals, Inc.
                                                            Office of
Healthcare & Insurance
September 28, 2018 Page 2
cc:       Darren K. DeStefano - Cooley LLP
FirstName LastName