He played 966 career NHL games, scoring 301 goals, 354 assists and 655 points.

During his active playing career, he played for 14 seasons, between 1987–88 and 2002–03, in the NHL for the New York Rangers, Minnesota North Stars, Dallas Stars, San Jose Sharks, Chicago Blackhawks and Washington Capitals.

On 15 April 1993, Dahlén scored the final goal in Minnesota North Stars history in a 5–3 loss to the Detroit Red Wings, Russ Courtnall and Dave Gagner assisted on the goal.

After his playing career, he has served as an assistant coach for the Swedish national team and a pro scout for the Dallas Stars; and in June 2006, he was hired as an assistant coach by the Stars.

[2] Following the 2007–08 season, Dahlén left Dallas to take the head coaching position for Frölunda HC in Elitserien in Sweden.