The 22-year-old Kim finished at 16-under 272 at Quail Hollow in Charlotte.
"It's been a wonderful week. I have to thank everybody who helped me get to where I am right now," Kim said. "It's been a long ride, but it sure is worth it."
Kim collected $1,152,000.
Ben Curtis shot a final-round 65 for second-place at 11-under 277 and Jason Bohn carded 71 to take third, another shot back.
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