McCarty captures first PGA Tour title in Black Desert Championship
The 26-year-old left-hander from Arizona saw his Korn Ferry Tour success translate quickly.
He was making his third career PGA Tour start but just his second since earning automatic promotion with three wins on the developmental circuit this year.
He became the first player since Jason Gore in 2005 to win on the PGA Tour in the same season that they were promoted via the three-victory route.
"To do it like this, I don't know how you can expect it," he said. "It was a lot of fun (and a) pretty surreal moment."
McCarty fired an eagle and four birdies against two bogeys on the par-71 Black Desert resort course, his 23-under total of 261 putting him three clear of Germany's Stephan Jaeger, who posted a 68 for 264.
McCarty started the day with a two-shot lead and with two birdies on the front nine was still two in front through 11 holes.
Then came some nervy moments with a three-putt bogey at the 12th and an errant tee shot on the way to a par at 13.
But McCarty pushed his lead to three strokes with an eagle at the short par-four 14th, where his tee shot bounced in front of the green and rolled within four feet of the pin.
He added an eight-foot birdie at the 16th and, after missing a short par putt at the par-three 17th, birdied the par-five 18th for the fourth straight day.
"It was good," he said. "Hard fought - a lot of tough pins with the wind picking up. (I was) just able to get my spots well enough and kind of hang in there and have a lot of stress-free pars."
US veteran Lucas Glover, whose six tour titles include the 2009 US Open, had nine birdies in his nine-under 62 that left him tied for third with Kevin Streelman (69) on 265.
Germany's Matti Schmid had seven birdies and an eagle in a 62 that left him alone in fifth on 266.