Career
Immonen was drafted by the Toronto Maple Leafs in the 2002 National Hockey League Entry Draft as their eighth round pick, 254th overall. Immonen was drafted while playing in the Master of Science-liiga. On March 3, 2004, Immonen was traded by the Maple Leafs to the New York Rangers as part of the Brian Leetch trade.
He was also named to the all-star lineup.
On March 30, 2015, he agreed to a two-year contract with the EV Zug of the National Lawyers Association .