Exhibit 24

             LIMITED POWER OF ATTORNEY - SECURITIES LAW COMPLIANCE

     The undersigned, as an officer or director of BlackLine, Inc. (the
"Corporation"), hereby constitutes and appoints Karole Morgan-Prager and Michael
Rauch, each the undersigned's true and lawful attorney-in-fact and agent to
complete and execute such Forms 144, Form ID, Forms 3, 4 and 5 and other forms
as such attorney shall in his or her discretion determine to be required or
advisable pursuant to Rule 144 promulgated under the Securities Act of 1933, as
amended, 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 Corporation, and to do all acts necessary in
order to file such forms with the Securities and Exchange Commission, any
securities exchange or national association, the Corporation and such other
person or agency as the attorney 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, are 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 Limited 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
Corporation unless earlier revoked by the undersigned in a writing delivered to
the foregoing attorneys-in-fact.

     This Limited Power of Attorney is executed as of the date set forth below.

                             Signature:   /s/ Owen Ryan
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                             Print Name:  Owen Ryan
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                             Dated:       August 10, 2018
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