The Durban-born Mabaso impressed during his first PSL season with Sundowns having been promoted to the senior team at the beginning of last season.
He appeared 23 times for the Brazilians last season, but the arrival of Ghanaian centre-back Rashid Sumaila and right-back Bryce Moon meant he could play no part this season.
MP Black Aces co-chairman George Morfou expressed his excitement at adding the 22-year-old Mabaso to his current squad.
“We are very excited to bring Mabaso on board, with two of his former teammates at Sundowns now with Aces. Abel will have ample time to acclimatise and get to know his new teammates,” Morfou was quoted on the Aces website.