The result means AmaZulu move up one place on the table to 12th with 28 points while Sundowns stay 11th on 32 points.
Chances came thick and fast in the opening 20 minutes and Usuthu had the first in the sixth minute when Njabulo Manqana provided a great cross into the box, which Andile Khumalo met, but his powerful header was high.
In the eighth minute Hlompho Kekana tried his luck from 30 metres, but his shot went over the crossbar.
Ayanda Dlamini had probably the best chance of the half when he met a right-side free-kick, but his header went agonisingly wide.
The match started to slow after that as both teams became a little more cautious in attack and opted to tighten up in defence.
AmaZulu’s Thamsanqa Teyise fired a thunderbolt goalwards from 30 yards out on the half-hour mark, but his effort went over the bar and the half ended all square.
The start of the second 45 saw both teams making immediate changes as Kagiso Senamela replaced Andile Khumalo for AmaZulu and Elias Pelembe replaced Themba Zwane for Sundowns.
The change seemed to benefit Sundowns better and they forced Tapuwa Kapini into a number of saves.
In the 54th minute he had to react quickly as Jabulani Shongwe took a 25-yard shot, tipping it over the crossbar.
In the 70th minute he was called into action again, this time producing a good stop to deny Tebogo Langerman from 12 yards out.
Thereafter, AmaZulu took control of the game and were unlucky not to get the win three minutes from time when Senamela forced Wayne Sandilands into a brilliant save from the edge of the box.