Hermann Beyer was born the son of a commercial clerk and a saleswoman and is the younger brother of DEFA film director Frank Beyer. After graduating from the Staatliche Schauspielschule Berlin, he made his acting debut in 1966 at the Maxim Gorki Theatre in Berlin. This was followed in 1971 by a theater engagement at the Hans Otto Theatre in Butttsdam and, from 1972, an eight-year stint at the Volksbühne Berlin under Benno Besson. From 1980 to 1983 he worked as a freelance actor. From 1983 to 1999 he was part of the Berliner Ensemble, before working again as a freelance actor at stages in Chemnitz, Weimar, Hamburg, Munich, Bern, Schwerin, Zurich and with the independent theater group Norton Commander. In 2008, he appeared at the Berlin Volksbühne in Die Maßnahme/Mauser, based on Bertolt Brecht, Hanns Eisler and Heiner Müller, and played the role of the husband in Henning Mankell's two-person play Treffen am Nachmittag at the Dresden Societaetstheater, alongside Irma Münch.
Parallel to his work at the theater, Beyer also appeared in film and television productions, initially as a supporting actor, as in the 1965 TV movie Woyzeck. From the mid-1970s on, his film and television activities increased, initially for DEFA and DFF, where he also worked with his brother, and later in all-German productions. Beyer also acted in filmsn by students of German film schools. In 2012 he received a nomination for the German Film Award for his supporting role in Andreas Kannengießers Vergiss dein Ende.