Exhibit 21.1

List of Subsidiaries of Upland Software, Inc. as of December 31, 2020

Upland Software, Inc./Logiciels Upland Inc.

Upland Software I, Inc.

Upland Software UK Limited

Omtool, Ltd.

InterFax Communications Limited

Return Fax 2000 Ltd

Data Guard Limited

Rapide Communication Ltd.

Rant & Rave Limited

Wire-E Limited

66099 Limited

Adestra Limited

Adestra Pty Limited

Altify Ireland Limited

Altify, Ltd.

Char Software, Inc.