Contracts have not been signed for the rematch, but the 135-pound bout is expected to headline UFC Fight Night, which will take place at Northeast Olympic Training Center in Fortaleza, Brazil.
ESPN ranks Assuncao and Moraes the Nos. 4 and 5 bantamweights in the world, respectively. They fought in June 2017, with Assuncao coming away with a split decision victory. The bout was Moraes' UFC debut.
Assuncao (27-5) has already built an impressive résumé and will look to cement a title shot in this five-round matchup. The Brazilian has won 11 of his past 12 contests, with the only loss coming to current champion TJ Dillashaw.
Moraes (21-5-1) has bounced back from the loss to Assuncao with three consecutive wins, including first-round knockouts of Aljamain Sterling and Jimmie Rivera. A former WSOF champion, Moraes trains in New Jersey under striking coach Mark Henry.
UFC's 135-pound division is in a state of limbo, as Dillashaw moves down in weight to face flyweight champion Henry Cejudo for the 125-pound title at UFC 233 on Jan. 26. Dillashaw's bantamweight crown is not on the line in that fight.