Mika Lehtinen began his career as a hockey player in his hometown in the youth department of TPS Turku , for whose professional team he made his debut in the SM-liiga in the 1993/94 season , preparing a goal in two games. In the following season , the defender was the first time Finnish champion with TPS. At the same time he played as a loan player for Kiekko-67 in the I divisioona, the second Finnish division, just like the following year . In 1996 and 1997 he was runner-up in Finland with TPS, while he won the first edition of the European Hockey League with his team at European level in the 1996/97 season . In the 1998/99 , 1999/2000 and 2000/01 seasons he won the Finnish championship three more times in a row with TPS Turku.
From 2002 to 2004 Lehtinen was on the ice for MODO Hockey in the Swedish Elitserien . He then spent a season in the SM-liiga with the Espoo Blues before returning to his hometown club TPS Turku from 2005 to 2007. After he had lost his place there, he joined the 2007/08 season, the Milano Vipers from the Italian Serie A1 on. After the club was dissolved, he moved to Asiago Hockey within the top Italian division . With his new club he was Italian champion in the 2009/10 season . In the 2010/11 season the Finn played for Asiago's league rivals HC Bozen . From 2011 to 2012 he ended his active career with the Austrian second division club VEU Feldkirch .