It was Maritzburg's first ever away league victory over the Brazilians and leaves Ernst Middendorp's side unbeaten after three matches.
The Team of Choice almost scored straight from the kickoff a right-footed shot by Cuthbert Malajila from 35-yards out missed to the left side.
In the fifth minute the Brazilians had an early chance of their own when Edward Manqele couldn’t connect properly with a right-footed shot from the right side of the box and his effort was saved by Maritzburg keeper Shu-Aib Walters.
In the 30th minute Hlompho Kekana played a one-two with Lebohang Mokoena, but his shot from 20-yards went wide and high of goal.
Four minutes later Sundowns thought that they had found the opening goal from a corner kick through the head of Wayne Arendse when the defender connected with a cross, but he saw his effort headed off the line by Maritzburg right-back Peter Petersen.
The visitors continued their attacking football and a minute before half time a shot by Malajila from right side of 12-yards was saved by Wayne Sandilands with his feet when it had looked like he was beaten.
United took the lead in the 70th minute, when Buckley unleashed a trademark left-footed shot from 12 -yards.
Four minute later the former Bafana winger made it 2-0 in when he linked up with up with Malajila and unleashed a shot from close range that Sandilands could not handle.
Sundowns showed some late fight when they grabbed a goal but it was too late to mount a fight back. Teko Modise linked up with Mushekwi and the Zimbabwean international scored with a well taken shot that from 12-yards out.
Sundowns: Sandilands, Masenamela, Daniels, Arendse, Mabaso, Kekana (Langerman 80’), Modise, Mokoena (Pelembe 66’), Moriri, Manqele (Baffour 49’), Mushekwi
Maritzburg: Walters, Petersen, Cloete, Booysen, Awal, Morton, Buckley (Booysen 84’), De Jongh, Yende (Evans 70’), Malajila, Mandaza (Smeekes 58’)