 Ostermeier began his theatrical career in 1990 acting under director Einar Schleef, one of his major inspirations, in his Faust project at Berlin's Hochschule für Künste.After the Faust project concluded in 1991, Ostermeier began studying directing at the Ernst Busch Academy of Dramatic Arts in Berlin where in 1992 he met his mentor Manfred Karge.From 1993 to 1994 Ostermeier acted as Karge's assistant director and also acted in Weimar and at the Berliner Ensemble.