Scott opened the second round of the two-day event three-strokes behind leader Justin Rose but ended up with a 7-under-par 71 Wednesday for a 36-hole total of 8-under 134.
Rose, who had four consecutive birdies to get to 8-under at one point, had a pair of bogeys and no birdies over the final 11 holes and ended up second at 6-under. He shot 69 in the second round.
Jason Dufner, with a 1-under 70, was third at 3-under for the tournament and Padraig Harington ended up 3-over after an even-par 71 in the second round.
Rose pushed his score to 8-under with birdies over Nos. 4-7 Wednesday and led Scott by four strokes. But Rose dropped back with a bogey at the ninth hole and Scott got within one stroke with birdies at Nos. 13 and 15. A 16th-hole bogey for Rose left him tied with Scott.
Scott grabbed the lead on the 510-yard, par-5 17th when he placed a 6-iron shot within inches of the hole for a tap-in eagle.
Scott won $600,000 for taking the event. Rose earned $300,000 while Dufner collected $250,000 and Harrington took home $200,000.
The Grand Slam of Golf is a two-day event in which the winners of the year's four major tournaments are invited. Scott won the Masters while Rose claimed the U.S. Open and Dufner took the PGA Championship. Phil Mickelson won the British Open but withdrew from the Grand Slam due to a scheduling issue. Harrington, last year's Grand Slam winner, replaced Mickelson.