Sobral (35-8) submitted Rameau Thierry Sokoudjou via a second-round brabo choke at Affliction’s final event on Jan. 24.
Mousasi (25-2-1), a former Dream middleweight champion, will make his U.S. debut against the Brazilian jiu-jitsu black belt. The 23-year-old Armenian-born fighter submitted Mark Hunt with a first-round armbar at Dream 9 on May 26.
The title bout will join two others on Strikeforce's Aug. 15 card. In the main event, Gina Carano and Cristiane “Cyborg” Santos vie for the first-ever Strikeforce 145-pound women's championship. Lightweight champion Josh Thomson will also tangle with interim champion Gilbert Melendez in a rematch of their highly regarded June 2008 tilt.