Choi was born in Yeongam County, South Jeolla Province, South Korea on March 19, 1979. He graduated from Gwangju Jeil High School in Gwangju, South Korea, in 1998. He attended Korea University in 1998 and was a member of the South Korea national baseball team that finished second in the 1998 Baseball World Cup. He was scouted and signed by Leon Lee, the father of former major league first baseman Derrek Lee. Coincidentally, he later was traded to the Marlins for Lee.

Beginning in 1999, Choi spent four seasons in the Cubs minor league system and was considered to be one of the organization’s top prospects. On September 3, 2002, Choi made his Major League debut against the Milwaukee Brewers and became the first Korean-born position player to play in the Major Leagues.

In 2003, Choi played in 80 games, hitting .218 with eight home runs and 28 RBI. He was the Opening Day starter for the Cubs, but suffered a concussion following a collision with teammate pitcher Kerry Wood on June 7, 2003. Choi went on the disabled list, and never reclaimed his starting role. After the season, he was traded to the Florida Marlins for Derrek Lee.

Choi represented South Korea in the 2006 World Baseball Classic, in which his most significant contribution was hitting a three-run pinch-hit home run against Team USA.

Choi spent the entire 2006 season with Pawtucket. He was designated for assignment August 1, 2006, while on Pawtucket’s disabled list and removed from Boston’s 40-man roster. Choi cleared waivers on August 11, 2006, and was outrighted to Pawtucket.

On December 1, 2006, Choi signed a minor league contract with the Tampa Bay Devil Rays where he was given a shot to be Tampa Bay’s everyday first baseman. Choi decided to return home after failing to make Tampa Bay’s 40-man roster after 2007 spring training.

On May 14, 2007, Choi signed with the Kia Tigers in the Korea Baseball Organization. In his KBO debut game, He went 0-for-5 against the Doosan Bears. Choi finished his first KBO season with a .337 batting average, 7 home runs and 45 RBI, playing in 52 games.

In 2009, Choi broke out offensively and became a star, rebounding from the slump. He helped the Tigers into title contention immediately, batting .308, blasting a pro career-best 33 home runs, leading the KBO league in runs with 98 and helping them win the 2009 KBO regular season. Choi was runner-up in home runs (33), RBI (100), and walks (103), 4th in slugging percentage (.589), 6th in on-base percentage (.435), and 11th in batting average (.308). Choi and Kim Sang-hyeon hit 69 home runs, and the two together are called the “CK Cannon”.

On December 11, 2009, he obtained his first KBO League Golden Glove Award in first baseman nomination.

In 2010, Choi had a .286 batting average, with 21 home runs, 84 RBIs, and drew 81 walks. Choi received an all-star selection and also participated in the home run derby, where he set the record for longest home run.

In 2011, Choi was limited to 70 games due to injury. Choi hit .281, with 9 home runs and 37 RBI.

In 2012, Choi hit .252, with 7 home runs and 42 RBI in another injury-plagued season.

In 2013, Choi hit .258, with 11 home runs and 42 RBI. After the season, he underwent knee surgery.