Kasten was born in Hannover, and has played rugby since 1986,[3] first for the SV 08 Ricklingen and later, after the club was unable to field a youth team, for the SC Germania List. In 2003–04 he spent a season with DSV 78 Hannover but left the club when it faced financial trouble, to join RG Heidelberg, where he won two German championships with the club, before moving to England, where he played for the Southend RFC.[4][5] In 2009–10, he returned to Germany, after suffering from injuries in England, and now plays for Heidelberger RK.
Tim Kasten is considered to be one of the best German rugby players, his father Ralf having played for Germany, too.[9]
In 2011, Kasten extended his contract with HRK for another three seasons.[10] In January 2013 he announced his retirement from the German national team, having played 34 times for the German XV.[11]
