Matt Gogel shot a 68 on Sunday and finished alone in third place at 15-under-par 273, followed by Robert Allenby, who also carded a 68 in the final round to finish at minus-14.
Maruyama was three ahead of Faxon at the start of the final round at Forest Oaks Country Club and the last 18 would be a two-man race. Maruyama and Faxon traded three birdies over their first five holes and with pars at the next three, the par-5 ninth would be a pivotal hole.
Maruyama drove left of a cart path at the ninth and laid up with his second coming up short of the putting surface in the right rough. He knocked his wedge over the green with his third and left himself with a difficult pitch.
Faxon found the fairway off the tee, then reached the green in two with a 5-wood. Maruyama flopped his fourth 45 feet past the hole and missed his par save. Faxon left himself with a five-footer for birdie and a chance to complete a two-shot swing. Faxon, one of the top putters in the game, burned the edge on his birdie try and settled for par and a one-shot shift with Maruyama, who bogeyed the hole.
'Does that change the whole scope of things if I make that?' Faxon said. 'I don't know. Maybe it wasn't in the cards.'
It wasn't in the cards for Faxon. Maruyama holed a short birdie putt at the 11th and the duo exchanged birdies at the par-5 13th.
At the par-5 15th, Faxon's third from the left rough fell 18 feet right of the target. He missed his putt right of the hole but Maruyama sank a five-footer for birdie to essentially seal the tournament. He was four ahead with three holes to play.
Faxon dropped a shot at the 17th to make the final margin five strokes.
The win on Sunday was Maruyama's third on the PGA Tour. His first victory came in the 2001 Greater Milwaukee Open and took last year's Byron Nelson Classic. Maruyama became the fourth player to win a tour event in each of the last three seasons, joining Tiger Woods, Justin Leonard and Jim Furyk.
'I wasn't expecting this kind of golf this week,' said Maruyama, who has battled through a neck injury this season. 'I'm really happy to be one of those players, to be listed with the big names. This big win gives me a lot of confidence.'
The win also gave Maruyama an $810,000 first-place check. He vaulted to 35th on the money list and with the top 30 making it to the Tour Championship in two weeks, Maruyama will try and make some cash next week in Disney World.
'A couple of weeks ago I was just trying to get to 125th on the money list,' said Maruyama. 'After this win, I can see the Tour Championship. That would be a big chance.'
For Faxon, it was another second-place finish, his fifth since his last trip to the winner's circle at the 2001 Sony Open in Hawaii. He shot a 68 on Sunday and gave the credit to Maruyama.
'He's obviously a great player,' said Faxon. 'He's won a lot in Japan. I think if putting is his weakness and he continues to putt well like this, I think he's going to do extremely well over here.'
Jay Haas (68), Brenden Pappas (66), John E. Morgan (67), Jonathan Byrd (68), Jeff Brehaut (68), Stephen Ames (69) and K.J. Choi (70) shared fifth place at 13-under-par 275.