Rask started his career in the youth teams of his hometown club SaPKo. He played in 26 games for the Tampere, Finland based Ilves jr. in the Finnish Junior League. His GAA was 1.86 with 2 shutouts and a .935 save percentage. He was the top ranked European goaltender in the 2005 NHL Entry Draft.
Tuukka Rask played his last European ice hockey season, as the number one goaltender for the Ilves Tampere (Tampere Lynx) team in the Finnish SM-Liiga. As of March 1, 2007, he sports a saving percentage of 92.94 (second in the league, among primary goalies), goals against average of 2.30 (fourth in the league), while facing 1356 shots (2nd most in the league).
On May 5, 2007, Rask signed a 3-year contract with the Boston Bruins, and was in attendance to observe the Providence Bruins's 2006–07 playoff run for the AHL's Calder Cup championship. The Providence team did not make it past the second round of the Calder Cup against the Manchester Monarchs, but Tuukka practiced with the Providence team briefly.
On November 5, 2007, Rask was called up from the Providence team to the Boston Bruins for the first time. Just two weeks later, on November 20, he recorded his first NHL win, a 4–2 "come-from-behind" victory, playing in a road game against the Toronto Maple Leafs.
October 3, 2008 - The Bruins assigned goalie Tuukka Rask to the Providence Bruins. Rask has the best save percentage (.952) among the goalies in preseason play, followed by Manny Fernandez (.875), Tim Thomas (.869) and Kevin Regan (.857). But it was decided to go with the 2 veteran goal tenders Thomas and Fernandez for the 2008-2009 season.