Carin Koch had a successful amateur career. She was Swedish Girl Champion in 1988 and played in the Junior and Senior European Amateur Team Championships as a member of the 1985-91 Swedish national amateur team. She was also 1990 European Team Junior Champion. Koch enrolled at the University of Tulsa and was named Second-Team All-American in 1990 and Scholar All-American in 1991. Between 1987 and 1991 she played eight times on the Swedish Telia Tour as an amateur, never finishing outside the top ten. She turned professional in 1992.
1992 was her rookie year on the Ladies European Tour. She gained 3 wins on the Swedish Telia Tour in both 1992 (including the Swedish Matchplay Championship) and 1993. In 1994, she finished fourth on the Asian Order of Merit and tied for fifth at the LPGA Final Qualifying Tournament to earn exempt status for the 1995 LPGA season.
In 1995, her rookie season, her best LPGA finish was a tie for second at the JAL Big Apple Classic. She also gained two top ten finishes on the LET Tour. In 1996 she almost gained her maiden LPGA victory losing the Edina Realty Classic to Liselotte Neumann in a playoff. In 1998 she gave birth to her first son, Oliver Michael Ture.
In the 1999 Jamie Farr Kroger Classic Koch had a two shot lead with just the final hole to play. Her caddie gave her the wrong club and she made double bogey to drop into a sixway sudden death playoff which was won by Se Ri Pak. In 2000 Koch won her maiden European title at the 2000 Chrysler Open. She was a member of the victorious European Solheim Cup Team, where she went 3-0 as a “rookie” and sank an eight-foot birdie putt on the 17th hole to win her match against Michele Redman to clinch the European Team’s victory. She also teamed with Sophie Gustafson to win the inaugural TSN Ladies' World Cup of Golf.
In 2001, she became an LPGA maiden winner at the LPGA Corning Classic. At the start of 2002, Carin topped a Playboy internet poll as the sexiest women on the LPGA but declined to pose for them nude. This was the year Koch recorded a career-best 13 top-10 finishes, including three runner-up finishes and was a captain's pick for the European Solheim Cup team. In 2003, Koch gave birth to her second child, Simzon Michael but still played well enough to be a captain's pick for the 2003 Solheim Cup won by the Europeans in her native Sweden.
In 2005, she won her second career LPGA event at the Corona Morelia Championship. and was again a captain's pick for the 2005 Solheim Cup. She teamed up with Sophie Gustafson to represent Sweden at the inaugural Women's World Cup of Golf and was also a member of the International team at the inaugural Lexus Cup. She also played in the 2007 Women’s World Cup of Golf with Helen Alfredsson.