He played three years for KalPa Kuopio in Finland before joining Clarkson University in 1991. The Edmonton Oilers chose him 205th overall in the 1992 NHL Entry Draft and brought him up at the ned of Clarkson's 1994-95 season for five games. That was the only time he played for the Oilers. Tuomainen spent the next two years in the minor pros and returned to Finland to play for HIFK Helsinki for two seasons. Tuomainen played for Finland in the 1992 World Junior Ice Hockey Championships and the 1998, 1999, and the 2000 World Championships.