Fresh off a six-shot triumph in the Australian Open in Sydney, the 21-year-old Spieth returned to American shores and finished off a wire-to-wire victory at the Isleworth Golf and Country Club.
It was Spieth's third professional victory, his second on the PGA Tour, but his first win on the US circuit in 72 holes - after his maiden triumph at the John Deere Classic in July 2013 came via a play-off.
Spieth carded a final-round six-under-par 66 in Florida, to finish on 26-under overall - well clear of Swede Henrik Stenson, who was the only other player to shoot in the 60s for all four rounds at the exclusive event.
Stenson rounded out his week with a three-under 69, to be 16 under and outright second.
Americans Patrick Reed (68) and Keegan Bradley (70) were one shot further back, while Australian Jason Day shot his best round of the week - 66 - to edge into the top five.
The story of the week, Spieth aside, was tournament host Tiger Woods and his struggles, with the 14-time major winner finishing tied for last in the 18-man field.
Woods was level with fellow American Hunter Mahan (75) at even par, but that was an achievement in itself - as the 38-year-old was propping up the leaderboard on his own throughout the week, but he finished with a 69-72 on the weekend.
Rickie Fowler (68) and Justin Rose (71) were tied for sixth on 11 under, 15 shots behind Spieth.
Two shots back at nine under were American trio Zach Johnson (69), Billy Horschel (67) and Matt Kuchar (70).