The hosts found themselves on the back foot with only five minutes played when Emiliano Tade fired in a superb shot from the edge of the area.
United came fighting back and Thabiso Kutumela had a shot which was turned around the post by for Sundowns keeper Denis Onyango.
However, the Team of Choice suffered another blow on 20 minutes when Gaston Sirino was afforded space in the box which allowed him to cross for Lebo Maboe to fire in a first-time shot from close range.
Again though Maritzburg showed character, and with the home fans at a packed Harry Gwala Stadium right behind them, they took the game back to the Brazilians and created a series of goal-scoring chances.
But Onyango had other ideas as he made a double stop in the 26th minute to keep out a Fortune Makaringe header, and also the follow up from the same player.
The Ugandan international then made another excellent reflex save to deny Yannick Zakri from scoring with a header after Makaringe’s cross.
Onyango was at it again six minutes later when he somehow got a foot out in time to deflect Zakri’s goal-bound shot wide of the target.
Maritzburg returned for the second half in a positive frame of mind, although they almost conceded a third when Rivaldo Coetzee’s close range shot from a corner went inches wide.
The Team of Choice were firmly on the front foot though and Makaringe when he went clean in on goal from a Kutunela dink, but shot straight at Onyango.
Masandawana were then reduced to 10 men on the hour mark after Sirino was booked for a foul and then shown a second yellow immediately after.
Sensing a comeback and with the crowd willing them on, United surged forwards looking for a goal, although again they escaped at the other end when Zwane shot wide with only Richard Ofori to beat.
However, all the action was happening in the Sundowns box and Maritzburg’s efforts finally paid dividends in the 82nd minute when Makaringe netted from close range after Onyango had dropped a Pogiso Sanoka cross before Zakri got a vital touch.
The closing moments saw the Eric Tinkler’s men camped out around the opposition box, but despite their considerable effort, it just wouldn’t fall for them in front of goal.
That meant that Maritzburg came up empty handed, although they can surely take positives from a very gutsy performance in a match in which they were on top for nearly the entire game bar the opening 20 minutes.
Maritzburg United: Ofori; Kunene, Xulu, Allie, Sanoka, Makaringe, Matsi (Mekoa 56'), Kutumela (Moseamedi 69'), Kateregga, De Reuck (Zakri 27'), Shandu.
Mamelodi Sundowns: Onyango; Langerman, Nascimento, Coetzee, Morena, Mabunda, Kekana, Zwane (Mahlambi 84'), Sirino, Tade (Lakay 64'), Maboe (Arendse 86').