Born in Frederiksværk, Christensen started his career with Danish club Lyngby BK.
In December 2001, he moved abroad to play for German club Hamburger SV in a DKK 500,000 transfer deal.
In July 2005, when his Twente contract ran out, Christensen moved back to Denmark on a free transfer to play for Brøndby IF.
He continued to come on as a substitute and scored his first goal in an away game at Charlton Athletic, an injury time equaliser earning his side a point.
[6] After Kim ended his career on the pitch, he decided to join his local childhood club FFK as a coach.