Billy Horschel outlasted former world number one Jason Day in a one-hole playoff at the AT&T Byron Nelson.
American Horschel shot a final-round one-under 69 in tough conditions to finish the tournament at 12 under on Sunday.
Australian Day carded a 2-under 68 to join him atop the leaderboard, but he bogeyed the par-four 18th during the sudden-death playoff.
The win - the fourth of his career on the PGA Tour - could not have come at a better time for Horschel, who came under some fire last week at the Players Championship when he appeared to toss his putter at his caddie.
Day was seeking his first win since last year's Players Championship. He had been dealing with back and personal issues this season, which had led to just one top 10 worldwide since last year's FedEx Cup playoffs opener.
Despite the loss, it appears Day has finally regained his confidence and form as major championship season approaches.
James Hahn finished third - a shot adrift - after bogeying three consecutive holes on the back nine.
He bounced back by hitting a tremendous approach shot on the par-four 18th, which led to a birdie. But he still posted a final-round 1- 71 to miss the play-off.
Jason Kokrak was a stroke behind, while Danny Lee (68), Sean O'Hair (68), An Byeong-hun (69) and Bud Cauley (70) were eight under.
World number one and U.S. Open champion Dustin Johnson was firmly in contention after 36 holes this week, but he got caught in quicksand over the weekend to finish tied for 13th at six under.
Masters champion Sergio Garcia was four over on the final day to finish eight shots off the pace.