Kim fired a bogey-free final round of three-under 69 to snatch the title at 10-under 278 at TPC at Sawgrass in Ponte Vedra Beach, Florida, on Sunday (local time).
At 21, Kim is the youngest player to win The Players Championship in its 44-year history. He was the only player who didn't commit a bogey in the final round.
This was Kim's second career PGA Tour win after the Wyndham Championship last August. He is the second Korean, after Choi Kyoung-ju in 2011, to win what's widely regarded as the "fifth major."
"I still can't believe I'm the champion, and I'm the youngest champion," Kim said. "I'm looking forward to working hard from now on."
The latest win is such a huge confidence booster that Kim said he's now looking forward to major championships.
"The difference between my first victory and this one is that I am now confident I can win a major," he said. "They say you need experience to do well at the majors, but if I can study the course beforehand and prepare accordingly, I think it's possible (to capture a major)."
Kim also soared in the world rankings, jumping from 75th to 28th. He's the second-highest-ranked Asian player after Hideki Matsuyama, No. 3 from Japan. The next South Korean on the list is Wang Jeung-hun, a three-time European Tour winner, at No. 57.
Kim started the day two strokes off two co-leaders: J.B. Holmes and Kyle Stanley. But Kim opened his final round with a birdie and then added two more at the seventh and the ninth to get to 10-under.
Kim then parred the treacherous back nine -- including the famous par-three 17th hole featuring an island green -- to clinch a three-shot victory over Ian Poulter and Louis Oosthuizen.
Kim didn't make things easy for himself, hitting only eight greens in regulation. But he had a stretch of six consecutive holes on the back nine without facing a par putt over two feet as he scrambled his way to the top.
Kim cashed in the $1.89 million winner's check, one of the largest on the tour, behind only major championships such as the US Open and the Masters. The victory catapulted Kim from 114th to 13th on the tour's money list with about $2.35 million.
On top of the financial windfall, Kim also received a five-year exemption on the PGA Tour and a three-year exemption to the Masters.
Kim said he drew inspiration from Choi, who still leads all South Korean players with eight career PGA Tour victories.
"From that moment (when Choi won the 2011 Players Championship), I was dreaming that I really want to be in this tournament," Kim said. "And I'm very glad I could practice with him. He gave me a lot of advice. That's why I could do well."
Kim also said he's been battling back pain since the start of the season. Now that he has more security with his playing status, Kim said he'll take better care of his body and try to play more aggressively when in contention.
"I've been striking the ball really well for about two or three weeks," Kim said. "I was confident that I could do well here as long as I had my short game in place. I put a lot of practice into my short game before the tournament and it all worked out in the end."
Kim recently changed his putting grip. He's now using the claw grip -- the left hand in a normal position and the right hand turned upside down with the palm facing the ground as if the player were holding a pencil -- after watching Sergio Garcia win the Masters with it last month.
"My father told me, 'If such a great player is using it, you should give it a try,'" said Kim, who's ranked 94th on the tour with 29.02 putts per round and tied for 155th with 1.795 putts per hole on average.
"I practiced that grip for about a week and it worked well at the Valero Texas Open (in April)," Kim added. "And it worked best whenever I got nervous. I was comfortable with it." (Yonhap)