POWER OF ATTORNEY

    The undersigned hereby constitutes and appoints Jean Liu, Todd Simpson and
Elizabeth Bekiroglu each of them, his or her true and lawful attorney-in-fact
to:

    (1) execute for and on behalf of the undersigned, in the undersigned's
capacity as an officer, director, and/or person who holds more than 10% of the
stock of Seattle Genetics, Inc. (the "Company"), Forms 3, Forms 4 and Forms 5 in
accordance with Section 16(a) of the Securities Exchange Act of 1934, as amended
(the "Exchange Act"), and the rules thereunder;

    (2) do and perform any and all acts for and on behalf of the undersigned
which may be necessary or desirable to complete and execute any such Forms 3,
Forms 4 or Forms 5 and timely file any such forms with the United States
Securities and Exchange Commission and any other authority; and

    (3) take any other action of any type whatsoever in connection with the
foregoing which, in the opinion of such attorney-in-fact, may be of benefit to,
in the best interest of, or legally required by, the undersigned, it being
understood that the documents executed by such attorney-in-fact on behalf of the
undersigned, pursuant to this Power of Attorney shall be in such form and shall
contain such terms and conditions as such attorney-in-fact may approve in his or
her discretion.

    The undersigned hereby grants to each such attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that such attorney-in-fact, or his or her
substitute or substitutes, shall lawfully do or cause to be done pursuant to
this power of attorney.  The undersigned acknowledges that the foregoing
attorneys-in-fact, in serving in such capacity at the request of the
undersigned, are not assuming, nor is the Company assuming, any of the
undersigned's responsibilities to comply with Section 16 of the Exchange Act.

    This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, Forms 4, and Forms 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 attorneys-in-fact.

    The undersigned has caused this Power of Attorney to be executed as of this
14th day of May, 2021.


                                        /s/ Clay Siegall, PhD
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                                        Signature