Born in Gudmundrå, Sweden, Grönhagen made his debut for Kramfors IF in Division 3 as a 15-year-old.
[3] Over eight seasons, he played 146 league games for Djurgården and scored 48 goals.
[6] In November 2003, it was announced that Grönhagen was to take over IF Brommapojkarna for the 2004 season.
[8] In September 2006, Grönhagen started his second tenure in Djurgårdens IF, taking over from Kjell Jonevret.
[9] He managed the team for the remaining six matches of the season[10] Grönhagen joined Norwegian Tippeligaen side Fredrikstad FK in 2007.