Tremmel left Bavaria in 2002 for spells at Hannover 96 then Hertha BSC, where he spent 2004–05 in the reserve side. He joined Cottbus in 2006 on a two-year contract and announced his intention to leave the club on 29 April 2010. On 7 May 2010, his transfer to Hertha BSC for the upcoming season was confirmed, but the transfer failed and he signed for FC Red Bull Salzburg on 20 May 2010.