KJ was born on May 19, 1970 in South Korea. He was born as the oldest son with two younger brothers and one younger sister. Both of KJ's parents were farmers on a small island called Wando, in the southernmost part of Korea. While attending his local highschool, KJ joined the powerlifting team. When KJ was only 13 years old he could squat 350 pounds, a feat for which he was later given the nickname Tank by fellow South Koreans. One day when KJ was 16, the powerlifting coach told the team to separate into two lines. One line would continue to practice powerlifting, and the other would begin to practice a sport called golf. Nobody in that golf line knew what golf was, including KJ, so he slyly left the golf line, thinking he had outsmarted his destiny and went back into the powerlifting line. Luckily the coach saw him change lines and demanded that he play golf. The coach gave KJ a single golf club and a book written by Jack Nicklaus called Golf My Way. From that day on, Golf My Way became KJ's holy grail, and he taught himself how to play golf. KJ lived more than 2 hours from the nearest golf course, so he would wake up at 5 a.m. every morning and take the bus to the golf course and practice. KJ would practice religiously until it got dark. Most of the people in KJ's community didn't know what golf was and tried to convince his parents to make KJ quit. People thought KJ was wasting his time, yet after 6 years of practice and 2 years serving the military, KJ became a pro golfer.
He turned pro in 1994, but did not join the PGA until 2000. Since turning pro, KJ has won a total of twenty professional golf tournaments worldwide, including eight on the PGA Tour. He is the most successful golfer in all of Asia.
His first professional win of his career was at the 1996 Korean Open. Soon after his win on the Korean Tour, KJ began to play in the Japanese Tour and won the Kirin Open and Ube Kosan Open in 1999 to qualify for the PGA. He became the first Korean to earn a PGA Tour card. KJ had a rough rookie season and had to requalify for the 2001 season, but since then, KJ has been a consistent performer and has never had to requalify since. In 2002 KJ became the first Korean to win on the PGA at the Compaq Classic of New Orleans with a 4 stroke lead over Dudley Hart and Geoff Ogilvy. He followed up with another win that same year at the Tampa Bay Classic and dominated over the whole field with a 7 stroke margin of victory over Glen Day. In 2003, he won the Linde German Masters on the European Tour (his first and only win on the European Tour) and the SK Telecom Open. Although KJ had no wins in 2004, he placed 3rd at the Masters (his best finish at the Masters) and tied for sixth at the PGA Championship (his best finish at the PGA Championship). In 2005, KJ won his third PGA victory at the Chrysler Classic in Greensboro and won it again as the defending champion in 2006. KJ's 2007 season was his breakthrough season. With a very solid beginning with an 8th place finish at the Mercedes Benz Championship and a 4th place finish at the Sony Open in Hawaii, KJ was on a roll. He continued to play well and won the Memorial Tournament hosted by Jack Nicklaus and the AT&T National hosted by Tiger Woods in a span of just over a month. These two wins and an 8th place finish at the British Open, 11th in the WGC Bridgestone Invitational, 12th at the PGA Championship, and 2nd at The Barclays put KJ in a very high position in the FedEx cup rankings, world rankings, and money rankings. His 2008 Sony Open victory in Hawaii put KJ as the top 10 golfer in the world. Unfortunately, in 2009, KJ suffered a back injury that lasted throughout the season and missed 9 cuts. Due to his over-par season, his rankings dropped significantly, but he slowly began making his comeback in his 2010 season placing 2nd at the Transitions Championship and 4th at the Masters. Finally in 2011, KJ had the biggest win of his career at the Players Championship. Later that year, KJ hosted and won his own tournament called the CJ Invitational. Since his win, KJ has had very modest 2012 and 2013 seasons. In 2012 KJ placed 5th in the Hyundai Tournament of Champions and 8th at the WGC Bridgestone Invitational as well as 1st place at the CJ Invitational as the defending champion.
KJ has donated over one million dollars through his foundation to charities all over the world and received the Charlie Bartlett Award which is awarded to a professional golfer for his or her unselfish contributions to the betterment of society.