WASHINGTON (AFP) - Australia's Aaron Baddeley rolled in a 28-foot birdie putt at the fourth play-off hole on Sunday to edge out South Korea's Kim Si Woo for the PGA Tour's Barbasol Championship in Auburn, Alabama.

Baddeley, who notched his fourth PGA Tour victory and his first since Los Angeles in 2011, was 11 strokes off the pace after 36 holes, but was just three shots adrift after the rain-disrupted third round.

With a five-under 66 in the final round, he joined Kim on 18-under 266.

Kim had made the biggest move of the day, firing an eight-under 63 that included seven birdies and an eagle, with his one bogey coming at the 18th on the Robert Trent Jones Trail Grand National course.

The two finished 72 holes one stroke in front of Michael Johnson, who played for nearby Auburn University and capped his professional debut with a final-round 65.

Venezuela's Jhonattan Vegas, who had opened a six-stroke lead at the halfway stage on the strength of a stellar second-round 60, closed with back-to-back rounds of one-over 72. He finished tied for fourth on 269, alongside Americans Richard H. Lee and Michael Thompson, who both shot 65, and Andres Gonzalez, who carded a 67.

Baddeley, 35, spun his club into the air after securing the win, which gives him a two-year exemption on the PGA Tour and a place in the PGA Championship, the final major of the year.

After a lacklustre 2014-15 season, he had been playing the US tour on past champion status only, fighting to earn a full exemption.

"It's been a long five years and it's been a tough road," said Baddeley, who exchanged a tearful hug with wife, Richelle.

"To be able to make that putt there to win - wow," he said. "I let the putter swing properly and it went right in the middle."

The field in Alabama were labouring opposite golf's biggest draw this week, the British Open won on Sunday by Sweden's Henrik Stenson.

Baddeley is the fourth Australian to win on the US Tour this season, joining Adam Scott, Jason Day and Greg Chalmers.