Mawson, who started from pole, looked to get an early reprieve when series rival James Golding went off at Turn 3 on the opening lap.
The reigning Australian Drivers' Championship then spent the next few laps establishing what looked to be a comfortable lead which, at its peak, was over two seconds.
However a broken wing element almost cost him the race win, bringing second placed Aaron Cameron into the game in the closing laps.
After a thrilling final lap battle Mawson was able to hold on, the gap at the flag just four-tenths.
“It was good to finally put on a show for S5000. It was a bit in tense from my seat, but it was a good, clean fight,” said Mawson.
“The front wing flag and element came off on the second last lap, and to be honest, I didn’t know how much to push in the medium to high speed corners.
“On the last lap, Aaron was on me and it was super intense to defend my position and keep the lead without risk.
“But full credit to him, it was clean and fair fight and it’s great to come away within the win.”
Former Supercars full-timer Zane Goddard came home third ahead of Nathan Herne and Tim Macrow.
Cooper Webster was sixth followed by Kaleb Ngatoa and Golding, who recovered to eighth ahead of Ben Bargwanna and Shae Davies.
The third round of the Australian Drivers' Championship continues with a second race tomorrow evening.
