The German finished with a 2-over 74 for a 7-under three-round total of 209, clear of nearest challenger Jay Haas.
Langer dropped shots at Nos 5, 7, 13 and 17 but had enough of an overnight advantage for victory.
American Haas had two bogeys and two birdies going out, but parred all nine coming in for second. His son, Bill, was third in the main Nedbank Challenge event midway through his third round.
Ian Woosnam was third in the seniors after a 72, while Mark Calcavecchia plummeted to seventh out of eight after finishing with a 13-over 85 that contained two triple bogeys.
Final scores in the 54-hole Nedbank Champions Challenge for senior
golfers that finished at the par-72 Gary Player Country Club on
Saturday:
209 - Bernhard Langer (Germany) 68 67 74 211 - Jay Haas (USA) 71 68 72 214 - Ian Woosnam (Wales) 73 69 72 217 - Jeff Sluman (USA) 74 70 73 223 - Sandy Lyle (Scotland) 74 72 77 224 - Tom Watson (USA) 74 75 75 225 - Mark Calcavecchia (USA) 71 69 85 227 - Fred Funk (USA) 76 77 74