POWER OF ATTORNEY

        The undersigned, as a Section 16 reporting person of Atara
Biotherapeutics, Inc. (the "Company"), hereby constitutes and appoints Jeff
Cislini, David Tucker, Nimit Arora, Mina Kim and Kim Merritt the undersigned's
true and lawful attorneys-in-fact to:

        1.     Complete and execute Forms 3, 4 and 5 and other forms and all
amendments thereto as such attorneys-in-fact shall in their discretion determine
to be required or advisable pursuant to Section 16 of the Securities Exchange
Act of 1934 (as amended) and the rules and regulations promulgated thereunder,
or any successor laws and regulations, as a consequence of the undersigned's
ownership, acquisition or disposition of securities of the Company; and

        2.     Do all acts necessary in order to file such forms with the
Securities and Exchange Commission, any securities exchange or national
association, the Company and such other person or agency as the
attorneys-in-fact shall deem appropriate.

        The undersigned hereby ratifies and confirms all that said
attorneys-in-fact and agents shall do or cause to be done by virtue hereof. The
undersigned acknowledges that the foregoing attorneys-in-fact, in serving in
such capacity at the request of the undersigned, is not assuming, nor is the
Company assuming, any of the undersigned's responsibilities to comply with
Section 16 of the Securities Exchange Act of 1934 (as amended).

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to the
Company and the foregoing attorneys-in-fact.

        The undersigned hereby terminates all prior powers of attorney regarding
the subject matter hereof.

        IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of June 22, 2019.


                                      Signature: 	/s/ Eric L. Dobmeier
                                                        Eric L. Dobmeier