Donald clinched the tournament after he won a sudden-death play-off with South Korean Bae Sang-moon and the American pair of Robert Garrigus and Jim Furyk.
The four finished the event locked at 13-under-par, just one stroke clear of another group of four players, on a heavily congested leaderboard.
Donald, who had closed with a bogey-free round of five-under 66, won on the first playoff hole when he drained a birdie putt from less than seven feet after a brilliant approach shot from around 157 yards out of the rough.
The win provided the 34-year-old with his fifth victory on the US PGA Tour and elevated him back to the top of the world rankings.
Donald had been number one until he was passed by McIlroy two weeks ago.
South African Ernie Els led the event for most of the final day before making bogey on each of the last two holes to miss out on the playoff by a shot.