Steffen established himself as a radio newscaster in the 1940s and worked frequently on stage as a character actor. Film credits include the Edgar Wallace "krimi" The Dead Eyes of London. As a dubbing actor, he was the German voice of Henry Travers in It's a Wonderful Life, Peter Cushing in From Beyond the Grave, Noah Beery Jr. on The Rockford Files, and bit parts on Columbo. He had a principal role in the German animated feature Felidae.