John made his first film appearance in the 1932 thriller The White Demon which also starred Hans Albers in the lead role.

However, in 1943 he was sentenced to death by the People's Court for espousing "defeatist views" after Goebbels became aware he had been making "jokes about Hitler".

John also played a Gestapo agent in Peter Lorre's only directorial outing, the German-language Der Verlorene in 1951.

Throughout the 1950s John often portrayed members of the Wehrmacht such as in Des Teufels General (1955), Hunde, wollt ihr ewig leben (1957) and Officer Factory [de] (1960).

In the 1970s John also made guest appearances on West German television crime shows including Derrick, Tatort and Der Kommissar.