MIAMI: Collin Morikawa fired a three-under-par 69 to clinch a three-shot victory at the World Golf Championships-Workday Championship in Florida on Sunday.

The 24-year-old PGA Championship winner -- who led by two after Saturday's third round -- relied on accurate iron play and nerveless putting to close out victory at the Concession Golf Club in Bradenton.

Morikawa's final round saw him finish on 18 under with a 72-hole aggregate 270, three shots clear of Viktor Hovland, Brooks Koepka and Billy Horschel on 15 under.

After an early stumble when he bogeyed the par-four second, Morikawa recovered his composure to play flawlessly thereafter.

A 195-yard second shot on the fifth hole left him with a seven-foot birdie putt which he duly rolled in to return to even for the round.

A deft bunker shot on the seventh set up another birdie chance which he converted and he made the turn at two under after making an 11-foot birdie putt on the ninth.

Another birdie putt on the 12th saw him move to 18 under overall and he then rattled off six straight pars down the stretch to bag the fourth PGA Tour win of a professional career that is still less than two years old.

"It shows that I can come out here and compete," Morikawa said after prevailing against a strong field that included nearly every player in the world's top 50.

"What a week. I was working on so much these past couple of weeks. My game felt so good, I'm just so excited right now."

Morikawa is now only the second player after Tiger Woods to win both a major and a WGC title before turning 25.