Schwartzel finished 72 holes at 17-under 271 for his ninth European Tour victory and third at this event, having secured his maiden win here in 2005.
"It's always nice to get a win and get some confidence up," said the 29-year- old Schwartzel.
Richard Finch, playing on a sponsor's invite after failing to retain his card at the end of the 2013 season, shot a 70 at Leopard Creek Country Club and ended alone in second place at 13-under 275.
Simon Dyson (67), Ross Fisher (69) and Romain Wattel (71) shared third place at 10-under, one shot ahead of Soren Hansen, who carded a 71 and took solo sixth at minus-9.
Magnus A. Carlsson (66) and Simon Wakefield (68) tied for seventh at 8-under, while Danny Willett (69) and Warren Abery (68) shared ninth at 7-under.
Last week, Schwartzel coughed up the lead during the final round of the South African Open Championship, stumbling to a triple bogey and a double bogey en route to a tie for fourth place.
Such was not the case on Sunday, although Finch managed to threaten early, as the Englishman erased Schwartzel's overnight lead with birdies at Nos. 1 and 3.
After four straight pars to open, Schwartzel awoke with a deft tee shot to tap-in range at the par-3 fifth, which he converted for birdie and a 1-stroke lead. That margin held at the turn, with the duo matching birdies at the sixth and eighth, where Schwartzel holed from 20 feet.
Finch failed to keep pace during the inward stretch, however, as he bogeyed the 11th and fell behind by a pair after an errant drive led to a penalty drop.
Schwartzel pushed his advantage to three shots with a birdie from eight feet at the 13th and the tournament was all but decided at the next, where Finch's approach from a fairway bunker hit rocks on the edge of the water and landed in a bush, leading to a double-bogey 6. Schwartzel made par there, extending his lead to five strokes, and although Finch birdied the 15th, the South African cruised home, parring out to cap his bogey-free victory lap.
"He got off to a fantastic start and mine was a little shaky," Schwartzel said of his playing partner Finch. "I know with this golf course out of experience that it's a long way from over and you just have to keep hitting good shots."
NOTES: Schwartzel became the first player to win the Alfred Dunhill Championship three times. In addition to his three wins at this event, Schwartzel was runner-up in the 2006, 2007, 2010 and 2011 seasons ... Schwartzel is the first player to successfully defend his European Tour title since Luke Donald at the BMW PGA Championship in 2011-2012 ... Finch last won on the European Tour in 2008, when he titled twice.