McLardy fought off strong final round charges from the overnight leader, Nic Henning and James Loughnane to clinch the title at 20-under-par 268.
The victory, his first since the Kalahari Classic in 1998, came on a warm and humid day at the Royal Swazi Sun Country Club, where ball striking was of primary importance.
Playing in the last group of the day, the 28-year old remained at par through the first five holes. At the 163-yard par-3 sixth he drove his tee-shot to within six inches of the hole and had to settle for birdie.
But this set up a birdie run that ran hot until the ninth and gave McLardy the outright lead at the turn at 16-under.
Both Loughnane and Henning launched strong challenges at McLardy over the last nine holes, but a crucial eagle followed at the par-5 12th that set up the victory for the Randpark professional.
McLardy hit driver, 7-iron and punched his second over the water to four feet from the hole on the long par-5 17th. He drummed home the advantage with a 60-footer for eagle and was left with an easy par at the last to sign for an unblemished 64.
'I got off to a solid start,' said McLardy. 'After I got through the first five holes on par, I almost hit a hole-in-one at the sixth. That kind of upped the confidence a bit.
'I was 16-under through the first nine and knew that I just needed to keep it together over the back. The two eagles were quite a surprise!'
'I am pleased with my consistency this week,' said McLardy, who lost his exemption on the Sunshine Tour last season, but with this victory, can look forward to a two-year exemption.
Henning claimed second place with his 68, while Irishman Loughnane finished third on 16-under-par.
Defending champion, Bradford Vaughan shared fourth with past champion, Marc Cayeux on 12-under-par.