Brendan Steele shot a three-under round of 69 to clinch the Safeway Open trophy for the second year in a row.
Starting the final round in third place, t he American rallied on the front nine, not dropping a single shot and claiming three birdies by the halfway mark.
An equally impressive performance on the 16th and a staggering 369-yard drive on the 18th led to two more birdies on the par-5 holes - and his third PGA Tour title.
The 34-year-old finished the competition 15-under and two strokes ahead of Tony Finau.
The 28-year-old Finau claimed an eagle on the par-5 fifth hole, meaning the fellow Americans went into the back nine in a tied position.
But a double-bogey on the par-4 14th meant he could not chase down Steele, ending the first PGA Tour event of the season 13-under.
Tyler Duncan, who surprised many by going into the final day in pole position, could not hold on to his one-shot lead as the chasing pack came to the fore.
Two birdies on the front nine were overshadowed by three bogeys on the opening three holes and two more on the 7th and 8th holes.
A more steady performance on the back nine was not enough to lift the PGA rookie, who ended the event 11-under, and in joint fifth position with Graham DeLaet.
Meanwhile, PGA veteran Phil Mickelson, who has won 42 events, finished in third place, with three bogeys spoiling his round.
One of the big movers on day three, the 47-year-old birdied on the par-5 16th to close in on Steele.
He was one shot adrift but a bogey on the 17th left him with too much to do, seeing out the day two-under 70 and 12-under overall.
Scot Martin Laird finished within the top 20 in joint 17th after an up-and-down performance, going round in 74 on the final day in Napa, California.