Kim turned professional in 2006 and after receiving a sponsor's exemption he finished in a tie for second on his PGA Tour debut at the 2006 Valero Texas Open.

In May 2008, Kim won his first PGA Tour tournament at the Wachovia Championship, defeating former British Open champion Ben Curtis by five shots.

[5] In July 2008, Kim won his second PGA Tour tournament at the AT&T National, defeating Freddie Jacobson by two shots.

At the 2009 Presidents Cup, Kim posted an impressive 3–1 record, which included a 5 and 3 victory over Robert Allenby in the Sunday singles match.

Kim lost to Ross Fisher in the finals of the Volvo World Match Play in October 2009 4 & 3 after once again beating Robert Allenby in the semi-finals.

He became only the fifth player in 30 years to have won three times on the PGA Tour before the age of 25, the others being Tiger Woods, Phil Mickelson, Sergio García and Adam Scott.

In June 2012, Kim had surgery after injuring the Achilles tendon in his left leg and was expected to miss 9 to 12 months.

[12] In April 2019, during an encounter with a fan in West Hollywood, California, Kim referred to his golf game as "non-existent".

[13] On January 1, 2021, Adam Schriber, Kim's longtime coach, posted a photo of the two in front of the Dallas skyline with the caption "2021 is going to be special".