Frandsen gained 23 caps for the Denmark national team between 1990 and 2003, and represented his country at the 1992 Summer Olympics and 1998 FIFA World Cup tournaments.
Frandsen joined fellow Danish international Jakob Friis-Hansen at Lille, and played four years at the club.
Frandsen stated his intention to only play in Denmark temporarily, and having won the 1995 Danish Cup with FCK, he moved abroad once again in August 1996.
Playing in the second tier of English football, he made his debut for the club in a 1–1 draw at Port Vale before scoring his first goal for Bolton in the following game against Manchester City.
He soon earned a reputation as one of the best players in English football playing outside the top-flight FA Premier League championship, and it was assumed that it would only be a matter of time before one of the bigger clubs came in for him.
Frandsen left Bolton Wanderers to join Wigan Athletic on a free transfer in June 2004, helping them get promoted to the Premiership, scoring once in the process against Brighton.
After his retirement Frandsen worked as a football agent in Denmark,[3] until he was named new assistant manager at HB Køge in June 2009.