MIAMI, 8 Mar 2015 (AFP) - The 30-year-old American claimed his first win in his fifth tournament back, shooting a three-under 69 to win the World Golf Championships-Cadillac Championship by one stroke at the Doral course.
Johnson called Sunday's victory the greatest moment of his career as it is his first title since taking a leave of absence to deal with what he called personal challenges.
"It has been a tough road," Johnson said. "But a lot of great things came out of it, including my son.
"I am so excited. This one is by far the best one."
Johnson finished with a nine-under 279 total, one stroke ahead of runner-up and fellow American JB Holmes and two clear of reigning Masters champ Bubba Watson in a battle of the longest hitters on the PGA Tour.
Holmes, who was seeking to finish off a wire-to-wire victory, shot a three-over 75 while Watson had a one-under 71 on the Blue Monster course.
Johnson has now won titles in eight consecutive seasons and earned his first since the 2013 WGC HSBC Championship.
He won for the first time since announcing last July he was taking a hiatus to deal with personal problems.
Johnson returned to the tour at the Farmers Insurance Open in February where he missed the cut by one stroke.
One month earlier, his fiancee Paulina Gretzky had given birth to the couple's first child, a boy.
Johnson parred the final hole Sunday then celebrated at the 18th tee with Paulina and his infant son. Paulina is the eldest daughter of hockey legend Wayne Gretzky.
Johnson missed the cut in two of his previous four starts, finished fourth at Pebble Beach and lost in a playoff at the Northern Trust Open.
"It feels so awesome to get that W," said Johnson, who was runner-up at the 2011 British Open. "I knew there was something missing from making me great. I have been working hard on that."
Aussie Adam Scott (71) and Swede Henrik Stenson (72) shared fourth place at four-under. South Africa's Louis Oosthuizen stumbled to a one-over 73 and ended alone in sixth at three-under 285. Bill Haas (74) and Webb Simpson (73) were one stroke back at two under.
Holmes, who led after each of the first three rounds, bogeyed three of four holes from the third. He played the final 12 holes in even-par to finish in sole possession of second place at eight under.
"Not what I hoped for, but so grateful to be in the hunt," said Holmes, who underwent brain surgery in 2011 to remove a piece of his skull to relieve pressure caused by a structure defect.
A runner-up finish could have been another good omen for Watson. Both times he placed second at this event he went on to win The Masters.
Watson got off to a flying start by making birdie on four of the first seven holes in the final round to grab a two-shot lead. But three bogeys on the back nine left him two back at seven-under-par 281.
World number one Rory McIlroy found water twice at the 18th before chipping in for double-bogey. He managed an even-par 72 and shared ninth place at one-under 287 with two others.
McIlroy, who made headlines on Friday when he tossed his three-iron into a pond, said he still has some work to do to get ready for The Masters which begins April 9.
"My inability to hit the ball right to left isn't something that you want going into Augusta," he said.
Leading final-round scores on Sunday at the World Golf Championship Cadillac Championship at Doral (USA unless noted, par-72):
279 - Dustin Johnson 68-73-69-69
280 - J.B. Holmes 62-73-70-75
281 - Bubba Watson 71-69-70-71
284 - Adam Scott (AUS) 70-68-75-71, Henrik Stenson (SWE) 69-71-72-72
285 - Louis Oosthuizen (RSA) 71-74-67-73
286 - Webb Simpson 74-69-70-73, Bill Haas 74-73-65-74
287 - Kevin Na 74-71-71-71, Rory McIlroy (NIR) 73-70-72-72, Ryan Moore 66-71-74-76
288 - Danny Willett (ENG) 73-76-71-68, Jim Furyk 70-73-76-69, Rickie Fowler 68-77-71-72, Ryan Palmer 71-70-74-73, Lee Westwood (ENG) 71-72-70-75
289 - Jordan Spieth 75-69-73-72, Marc Warren (SCO) 73-75-69-72, Brandt Snedeker 74-73-70-72, Brooks Koepka 69-74-73-73, Morgan Hoffmann 73-71-71-74, Shane Lowry (IRL) 71-74-70-74
290 - Gary Woodland 70-74-76-70, Hideki Matsuyama (JPN) 76-72-72-70, Thomas Aiken (RSA) 78-69-72-71, Ross Fisher (ENG) 78-71-69-72, Matt Kuchar 73-75-70-72, Brendon Todd 72-73-72-73, Mikko Ilonen (FIN) 78-72-67-73, Patrick Reed 71-73-71-75