Bornwell Mwape had given Usuthu a 10th minute lead via his deflected shot, but that was cancelled out deep into first half stoppage time when former Bafana Bafana striker Mabhudi Khenyeza powered in an equaliser.
Then with 20 minutes to play, Roscoe Pietersen scored an own goal after a good cross by substitute Deon Hotto as the National First Division (NFD) outfit inflicted more misery on the AmaZulu, who are bottom of the top-flight league.
The host Usuthu made a bright start with strikers Ayanda Dlamini and Mwape both coming close inside the opening five minutes — the former cutting through the middle before firing agonisingly over and the latter prodding over.
At the other end Thembela Sikhakhane dragged an effort wide from just outside the box, before the opener arrived in a similar fashion to Ayanda’s earlier effort.
This time it was Mwape who carried the ball forward, before the Zambian saw his low strike from the edge of the box deflect off Nkanyiso Cele and beat Maximillian Mbaeva to the left corner.
Usuthu had a strong penalty appeal waved away by referee Thabo Nkosi before the half-hour mark as Sadat Ouro-Akoriko went down under a challenge from Nkanyiso Mngwengwe.
The hosts had another chance not long after, but Sifiso Hlanti’s drilled free-kick from the right was well caught by Mbaeva.
Abafana Bes’thende had their best chance of the game in the 32nd minute when winger Sibusiso Sibeko cut the ball back from the right to Matome Mathiane, who just had to hit the target from 12 yards out, but instead skewed wide.
However, the men from Umlazi had their equaliser in the referees additional time after Sibeko was brought down on the edge of the box. Khenyeza stepped up to arrow the ball beyond Energy Murambadoro into the top right corner.
Arrows were buoyed by that goal and after the restart twice came close to taking the lead.
First Khenyeza saw another clever strike deflect wide, before Zukile Mkhize forced Murambadoro to tip over after the corner that followed.
And again Arrows’ pressure was rewarded as they took the lead after 70 minutes when Pietersen’s attempts to clear Namibian Hotto’s cross from the right flew beyond a helpless Murambadoro.
AmaZulu hardly looked like they would equalise, but did have a chance at the death when replacement Asive Langwe shot just over with the goal gaping as Arrows held on for a memorable win.