The goals came from Tsweu Mokoro, James Chamanga and James Mayinga for Swallows, while Siyabonga Mkhwanazi netted a brace for AmaZulu.
The home side took the lead after just three minutes when Japhet Zwane fed Mokoro in the box, and the winger unleashed a powerful shot that gave Lawrence Ncala in the AmaZulu goal no chance.
But AmaZulu were seeing more of the ball and should have grabbed a deserved equaliser when Dumisani Ngwenya found space in the box, but his first touch let him down and Swallows stopper Greg Etafia was able to clear the danger.
They were level on 19 minutes, however, when a free-kick found Mkhwanazi, making his first start for Usuthu, and the youngster bundled the ball home, though there was a suspicion that the ball may have come off the defender last.
That joy was short-lived as the form striker in the Premiership, Chamanga, who had scored seven goal in his last two games, was given too much room on the edge of the area and drilled the ball into the back of the net from 25-yards, though Ncala appeared to get a hand to the ball and might have felt he should have saved it.
Ngwenya somehow missed a guilt-edged chance to draw the visitors level again when Thabo Mabaso’s cross evaded everybody and the striker has a simple tap-in to score, but miscued the ball and the danger was cleared.
Mkhwanazi then missed a free header late in the half as Usuthu finished the stronger of the two sides.
But he made up for that with a stunning leveler on 55 minutes from 30 yards after being played in by John Moshoeu.
But the home side scored a stunner themselves just three minutes later through James Mayinga, a goal which proved the winner on the day.
Mayinga found space in the box and drilled the ball home from 20 yards to score his first goal for the club.
Neither side could find a goal after that as AmaZulu pushed forward in search of an equaliser, and Swallows hung back, defending what they had.
The win moves Swallows into fourth, just three points behind table-topping Ajax Cape Town, while AmaZulu lie in 11th.