DeChambeau won for the fourth time in his last 12 starts on the PGA Tour and moved to No. 5 in the world ranking.
He had to survive a wild back nine at the TPC Summerlin in which four players had a share of the lead at some point. Cantlay, trying to become the first player to win back-to-back in Las Vegas in nearly 20 years, made a 15-foot birdie putt on the par-5 16th hole to take a one-shot lead. But from a bunker right of the green on the par-3 17th, Cantlay was fooled by the amount of sand under his ball and flubbed the shot.
One hole behind him, DeChambeau rolled in his long eagle putt from just off the green and celebrated with a big uppercut. Cantlay missed his long par putt, giving DeChambeau control of the tournament.
Cantlay birdied the 18th for a 65, but it wasn’t enough when DeChambeau played the final two holes conservatively for pars to finish at 21-under 263.
The 25-year-old American began his big run with a playoff victory at the Memorial, and then won consecutive FedEx Cup playoff events in New Jersey and Boston. He said he was playing Las Vegas to shake off a little rust, and it turned into another victory.
“I was able to play some great golf,” DeChambeau said. “I’m happy to get it done.”
Not since Jim Furyk in 1998-99 had anyone successfully defended his title in Las Vegas, and Cantlay looked as if he might get it done when he drove the green on the par-4 15th for a two-putt birdie, and then rolled in another good birdie after having to lay up on the 16th.
“When I dug my left foot in, it didn’t have a bunch of sand,” Cantlay said. “I hit the shot and there was more sand under the ball. I didn’t anticipate it.”
He wasn’t the only player stung by the outcome.
Former U.S. Open champion Lucas Glover had a 4-foot birdie putt on the 15th hole that would have given him a share of the lead with three holes to play. Glover missed the putt, and then missed a 30-inch par putt. One hole later, he was three shots behind.
Glover finished with a triple bogey for a 71 and tied for seventh.
Peter Uihlein, who shared the 54-hole lead with DeChambeau, didn’t make a birdie until the 11th hole, finished bogey-bogey for a 75 and tied for 23rd.
Rickie Fowler (63), Abraham Ancer (66) and Robert Streb (68) were another shot behind.
DeChambeau won for the fifth time in just his 68th start as a pro on the PGA Tour, dating to his victory in the John Deere Classic in 2017.