Bellator officials announced the 185-pound title fight on Monday. The Bellator 200 event will take place at SSE Arena, Wembley in London.
"Bellator continues to place a huge emphasis on its expansion into markets around the globe and creating a strong presence in the U.K. is a very important part of that," Bellator president Scott Coker said in a released statement.
Mousasi (43-6-2) has been a shoo-in middleweight title challenger since he signed with Bellator last year. The former UFC and Strikeforce veteran is the No. 5 middleweight in the world, according to ESPN's rankings.
The Dutch middleweight earned a narrow decision win against Alexander Shlemenko in his promotional debut in October.
Carvalho (15-1) has flown widely under the radar, despite his status as Bellator's official titleholder.
The 31-year-old Brazilian won the vacant belt in 2015 and has recorded three successful title defenses.