A goalkeeper, he spent his entire playing career with Hertha BSC.

He led Hertha BSC's amateurs to the 1993 Cup final, losing to a lone Ulf Kirsten strike, 15 minutes from time.

For most of his topflight career, however, he was only second-choice to Hertha, successively to Gábor Király and Jaroslav Drobný; his best years came in 2004–07, before the Czech's arrival.

On 2 August 2008, in a test match against Newcastle United, Fiedler sustained a serious injury, which ultimately forced him to retire at the end of the 2008–09 season.

On 1 July 2009, he began working as goalkeeper coach for Hertha,[4] having totalled 234 matches (both major divisions combined).