UFC president Dana White announced on Saturday the fight is scheduled to headline a UFC 179 pay-per-view event on Oct. 25 at Ginasio do Maracanazinho.
The title bout was originally supposed to headline UFC 176 on Aug. 2 in Los Angeles, but was postponed after Aldo suffered a non-severe neck injury. The entire event was eventually scrapped due to the loss of the main event.
It will mark the second time Mendes (16-1) will challenge Aldo for the belt in Brazil. Aldo won that fight via knockout with one second remaining in the first round.
Aldo (24-1) will seek the seventh defense of his belt. He is coming off a dominant unanimous decision over Ricardo Lamas at UFC 169 in February.
Since the first Aldo meeting, Mendes has won five consecutive fights including four by knockout. He defeated Nik Lentz in his most recent fight via unanimous decision, at a UFC on Fox event in December.