The bout, reported earlier by the Los Angeles Daily News, will serve as the pay-per-view card's co-main event and will mark the second meeting between the two middleweights. Mousasi defeated Souza via first-round knockout in the 2008 DREAM middleweight grand prix finals in Saitama, Japan.
Souza (20-3) demanded a big-name opponent following his most recent win over Francis Carmont. Souza won the February bout by unanimous decision. A former Strikeforce middleweight champion, he is 3-0 in the UFC, with wins over Carmont, Yushin Okami and Chris Camozzi.
Mousasi (35-4-2) is coming off a first-round submission victory against Mark Munoz at a UFC Fight Night event in May. The 28-year-old is also a former titleholder in Strikeforce as a light heavyweight. Since returning to the middleweight division earlier this year, Mousasi is 1-1 in the UFC. The loss came via unanimous decision to Lyoto Machida in February.
Souza and Mousasi are ranked by ESPN.com as the Nos. 4 and 9 middleweights in the world, respectively.