Elias Ngwepe and Fadlu Davids scored for the Team of Choice, with Pere Ariweriyai netting for Usuthu.
AmaZulu enjoyed the better start to the first half, which was a rather dull affair, and created two goalscoring opportunities, with the first chance arriving in the sixth minute when Bradley Ritson sent a superb cross into the Maritzburg United area, but striker Myron Shongwe produced a shocking header, which was cleared by the United defence.
Ritson was then sent clear in the 14th minute, but the striker slipped just as he was about to shoot and sent his effort well wide of goal.
The hosts created their first chance of the game in the 33rd minute when Sipho Mngomezulu saw his shot, from an acute angle, comfortably saved by Kakonje Kalililo.
The match remained goalless at the break.
Ritson should have put the visitors ahead three minutes after the restart when he got on the edge of a low cross from the right, but the striker sent his effort high over the crossbar from just six yards out.
Maritzburg United took the lead in the 58th minute when Kalililo, who ran to the edge of his goal area, produced a poor clearance which fell to Mngomezulu, whose first time shot, from close to the touchline, flew straight into an empty net as the AmaZulu keeper struggled to get back to his goal.
The hosts extended their lead two minutes later when they were awarded a free-kick on the edge of the Usuthu goal area, with Davids curling the ball around the wall and into the far corner.
AmaZulu then dominated the remainder of the game and deservedly pulled one back in the 83rd minute when Pere Ariweriyai headed home from a corner.
Shongwe should have leveled matters two minutes from the end when he ran clear, but his tame effort was comfortably collected by United keeper Hunter Gilstrap, and with that went the last chance of the game.
The result moves Maritzburg United up to second place in the log, on eight points from four games, while Usuthu remain 12th on 3 points from three games.