It was the second European Tour title for van der Walt but he said winning this week was especially important for a South African golfer coming so near to the death of South African statesman Nelson Mandela, for whom the event is named.
"It's obviously really special, making you a part of history," van der Walt said.
"Winning the Nelson Mandela at this time, when it's sad for everyone, everyone is mourning and tomorrow's the big day, it means a lot and it's something I can keep close to my heart forever."
The tournament started a day early -- Wednesday -- out of respect for to Sunday's services for Mandela, who died Dec. 5 at age 95. Soggy weather conditions limited play Wednesday and Thursday, however, and led organizers to cut the event to 54 holes.
Van der Walt had a second-round 62 that left him three strokes behind second-round leader Daniel Brooks. He was even after 11 holes -- with three birdies and three bogeys -- but rolled in a 30-foot eagle putt at the 558-yard, par-5 12th to take the lead. Birdies at 13 and 15 gave him the cushion to finish off the win.
He wound up at 15-under 195. Matthew Baldwin and Jorge Campillo, who each shot 68 Saturday, tied for second at 13-under. Romain Wattel, with a third-round 67, took fourth at 12-under and Oliver Bekker finished fifth at 11-under after a 69 Saturday.
Brooks staggered through a 6-over 76 Saturday. He was 6-over through seven holes and dropped into a tie for 11th.
Dennis Rodman pledges to end trips to North Korea
Scarlett Johansson steps out with fiance after pregnancy reveal