Lehlohonolo Majoro scored a brace of goals in the first half for AmaZulu, with Tangeni Shipahu grabbing a winner in the second half.
Katlego Mphela and Lionel Mutizwa got Sundowns' goals in the second half.
In what can be best described as a game of two halves, the visitors were in sublime form in the first half as they tore down the Sundowns defence at will from the first whistle.
The Brazilians hit back in the second half and cold have pulled away with the glut of chances that came their way, but it was not be as Shipahu produced the sucker punch in the dying minutes.
Though Sundowns will continue to lead the PSL standings, this result will be well received by the chasing pack.
Namibian striker Tangeni Shipahu, who was one of the star performers in AmaZulu’s 4-0 win against Mpumalanga Black Aces on Sunday, should have given his team the lead as early as the fourth minute.
Defender Siyanda Xulu gifted Shipahu a clear run at Wayne Sandilands in the Sundowns goals by missing an easy clearance. But the striker shot hopelessly wide when he had the goal at his mercy.
However, continued pressure from the visitors yielded a goal for AmaZulu when Sibusiso Hadebe’s precise pass from the centre of midfield cut open the Sundowns defence and fell perfectly for team mate Lehlehonolo Majoro.
The striker who bagged a brace of goals against Aces, controlled the ball expertly and fired coolly past Sandilands in goals.
Majoro doubled the Usuthu’s advantage after linking up with Shipahu in a move that started in AmaZulu’s own half. Once again, Majoro was able to finish with aplomb.
From a rare Sundowns attacking move, striker Nyasha Mushekwi hit the side netting near the half hour mark.
Surprise Moriri was the only other Sundowns player to get a shot at AmaZulu goals. In the 43rd minute, he fired a header which required Mbongeni Mzimela to tip over his crossbar.
The three changes made by Sundowns at the start of the second half transformed the Brazilians, who went all out to claw their way back into the game.
They got just the break they were looking for when they were awarded a penalty in the 51st minute. Katlego Mphela who came on as a substitute pulled back one for the hosts.
From then onwards it looked certain that Sundowns would draw level and possibly pull clear as they were completely dictating play.
Mabhuti Khenyeza should have restored parity when he had clear sight of goal in the 59th minute, but he hit his volley onto the AmaZulu crossbar.
However, the Brazilians eventually drew level in the 77th minute when a Lionel Mutizwa volleyed home during a goalmouth scramble.
With the stage set for the Sundowns to pull off a memorable comeback, it was the visitors who claimed the spoils when Shipahu finally managed to find the back of the net in the 90th minute with a lobbed effort.