Grace hoisted the Nedbank Golf Challenge trophy with a final round 66 to claim a one stroke victory over 54-hole leader Scott Jamieson.
The South African started the day three shots behind Jamieson but made three birdies in his opening six holes and by the time he reached the turn was sharing the lead with the Scotsman.
The pair remained locked with three holes to play but Grace produced the knockout blow at the par-3 16th with a 40-foot birdie bomb that ultimately proved the difference.
THE TOURNAMENT TURNED AT THE PAR-3 16TH:
"This is awesome," Grace said in the aftermath.
"This is the one event that as a South African you want to win. It's Africa's Major for a reason and what a special place it is.
"There's a lot of history and a lot of great winners on the trophy and I'm very glad to be able to put my name on the trophy as well.
"I had to stay patient and I had to take the chances when they came my way. I missed a couple of short ones but I think the big key was the putt on 16."
36-hole leader Victor Dubuisson was third, a shot behind Jamieson, with China’s Li Haotong fourth following a blistering final round 65.
Jamieson was philosophical about the close call saying he was proud of his performance under pressure.
“Played with some of the best players in the world this week and proved that I can compete with them,” he said.
“So hopefully I can take something out of it. That was the goal coming here: to try and get into Dubai.
“I needed really top eight or something to do that. Second's pretty good."
Race to Dubai leader Tommy Fleetwood, who could have wrapped up the season-long competition with a win this week, fought his way into the top 10 after a poor start to the week.
The Englishman will heads to the final event of the season, the DP World Tour Championship in Dubai, with a 256,737-point lead over the in-form Justin Rose.
“It is what it is,” Fleetwood said after a closing 71 that saw him finish T10.
“I've played brilliant all year. I think to be in with a chance of winning the Race to Dubai, it's pretty special, really. It's not a burden.
“I don't feel stressed about it, I don't feel anxious. I just think it's great that I've got the chance to win it and a good chance.
"And as much as it depends on what they do, it is in my hands. I can take it out of everybody's hands but we'll see.
"I don't know how I'll feel next week. It's going to be a new experience, it's going to be a great experience. Playing in the Race to Dubai is very, very special and it's something that actually very few people get the chance to do.”
The Australasian challenge never materialised in South Africa with Sam Brazel claiming top honours in the group at 4-over and T42.
Ryan Fox was two shots further back and T52 while Scott Hend, who hit back from a tough opening 80 with a third round 68, cooled again with a Sunday 75 to end the week T57.
Andrew Dodt was the last of the group in the 72-man field but finished in last place at 18-over with rounds of 78-77-74-77.
SIGNATURE HOLES - 15TH AT MAGENTA SHORES (NSW):
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