Lidoda Duvha took the lead through Nkosiyabo Xakane early in the second half but two late strikes from Mandaza saw United taking maximum points from a game where they created more chances.
United came close to taking an early lead in the third minute when Ayanda Mtshali failed to hold on a swerving freekick from Dillon Sheppard, but the goalkeeper redeemed himself by stopping Philani Zulu from nudging in the rebound.
The Team of Choice continued to keep Leopards pinned in their half with Terrance Mandaza shooting just wide of the far post in the 13th minute, while Sheppard also shot over the target in the 29th minute.
Rodney Ramagalela and Amidu did find some spaces between the United defence at times, but they didn’t have the support around them to force Shu-aib Walters into making a save.
Mtshali on the other hand was kept busy at the other side, diving low to his left to keep out a low strike from Zulu in the 33rd minute, before producing an acrobatic save to deny Delron Buckley three minutes later.
United had more opportunities to take the lead before the break, only for Mandaza to send his shot inches over the crossbar in the 38th minute, before heading wide of the target seven minutes later.
Leopards then started the second half brightly, with Raymond Monama forcing Walters to palm his corner over the crossbar in the 47th minute, while Abbas Amidu shot against the sidenetting five minutes later.
The goal did arrive in the 56th minute as Xakane side footed an Amidu cross into an empty net after Walters had made a meal of another corner from Monama.
United almost drew level in the 65th minute when Ruben Cloete was left free to connect with a free-kick from Buckley, but Mtshali was positioned correctly to stop his header on the line, while Mohamed Awal volleyed over the crossbar two minutes later.
The hosts continued to push forward in search of the equaliser but in the 71st minute Michael Morton skewed his shot wide of an open net after Mtshali had come off his line to block an effort from Buckley on the edge of the area.
Ten minutes later Buckley clipped his freekick across goal but Awal failed to head in from close range while Mandaza also failed to nudge the ball in at the far post.
However, Mandaza made up for his earlier misses in the 84th minute as he volleyed home from close range after he was set up by a well-directed header from Sheppard.
The Zimbabwean international grabbed his brace just two minutes later, this time curling the ball beyond Mtshali’s reach from outside the penalty area to hand his side maximum points.