The former British Open champion beat Van der Walt by two shots afterclosing with a 6-under 67 for a 27-under total of 265 at the season-openingEuropean Tour event.
Van der Walt shot a 69 to finish one shot ahead of Retief Goosen , who alsocarded a 69 at East London Golf Club.
Oosthuizen and Van der Walt were tied with two holes to play butOosthuizen’s birdie and Van der Walt’s bogey at the short par-3 No. 17 finallyseparated the pair.
It was the 29-year-old Oosthuizen’s fourth European Tour title and firstsince his win in East London in 2011, while Van der Walt again missed out on afirst professional victory.
Oosthuizen had an up-and-down front nine at the par-73 course with an eagle,four birdies and two bogeys. But he birdied Nos. 11 and 17 and didn’t drop anyshots coming home to claim the $201,000 winner’s check.
Van der Walt opened with three straight birdies and had five in all. Hisonly bogey of the day was the crucial slip at No. 17, where he missed a birdiechance and a short putt for par.
“It was a real dogfight for most of the day,” Oosthuizen said. “Whathappened on 17, it was going to be one of us who faltered. If I two-putted, hewould probably have made that short putt.
“One of us needed to make some big putt to put a lot of pressure on theother guy and it was just fortunate for me that it went my way.”
Goosen, who won the Africa Open in 2009, managed an eagle and three birdiesbut dropped a shot at No. 10 and finished alone in third, one clear of Jaco vanZyl (66).
Scotland’s Alastair Forsyth was fifth to break up a run of South Africans atthe top of the leaderboard. Another South African, Richard Sterne , closed with a3-under 70 for 20 under and sixth in his first tournament in nearly a year afterstruggling with major back problems.