The 23-year-old, who is the son of former world top-10 tennis professional Jay Berger, served up a three-under-par 67 to clinch his first PGA Tour victory.
He finished at 13-under 267 at TPC Southwind, with Phil Mickelson (67), Brooks Koepka (66) and Steve Stricker (67) equal second on 270.
"It's the greatest feeling," Berger told Golf Channel.
"You work so hard to get here and to finally be able to put the trophy up ... I'm just thrilled right now."
Berger, who arrived at the event ranked 46th in the world, credited his sporting family background with helping him cope with the pressure of leading.
"I'm just a competitor. I got off to a terrible start today (with a bogey at the first hole) and I just grinded it out and was able to get some putts to fall."
Berger will head to Oakmont for the US Open that starts on Thursday brimming with confidence, as will Mickelson after his joint runner-up finish.
