Mackenzie Hughes birdied the second play-off hole on Sunday to defeat Sepp Straka and win the Sanderson Farms Championship in Jackson, Mississippi.
The Canadian won his second PGA Tour title and his first since 2016.
Seamus Power couldn't reproduce his form from Saturday as he shot a third 71 of the week to tie for 30th.
A birdie on the first was followed by a bogey on the third, before the Waterford native parred his next seven holes.
An up and down day then saw him hit three birdies and two bogeys over the next five holes to finish on 8 under par.
Hughes meanwhile began the day one shot off the pace set by Mark Hubbard. Hughes' final-round 69 got him to 17-under-par 271 for the tournament. The Austrian Straka was in the clubhouse at 17 under following a 67.
Both players replayed the par-4 18th hole at the Country Club of Jackson and saved par the first time. On the second playthrough, Hughes landed his approach shot eight feet away from the pin, and after Straka missed a longer birdie putt, Hughes knocked his in, pumping his fist just as his ball fell.
"I'm over the moon," Hughes said. "I had some moments today where I was tested and was able to pull through. It's kind of my M.O. a little bit ... to scramble and save some pars. I had to do that a little bit today on the back nine. Yeah, did everything I possibly could, just grinded my butt off, and luckily it was good enough."
Hughes made four birdies and one bogey during his round. He saved par at the1 8th to ensure the playoff, two-putting from 103 feet across the green.
"You just don't practice putts that long," Hughes said. "It was super fast. I just kept telling myself that I was going to two-putt that putt. I was going to get down there and I was going to make it."