Born in Berlin, he was a trained carpenter and commercial artist. The entertainer Harald Juhnke was one of the sponsors of the curly headed entertainer. In 1959 Dahlen made his cinema debut in Kurt Meisel's comedy "Love forbidden - marriage allowed". In 1964, Dahlen's career began in television. The actor, also known in Switzerland and Austria, has appeared in more than 35 feature films. He stood in front of the camera with Loni von Friedl, Elke Sommer, Claus Biederstaedt, Rolf Becker and Willy Millowitsch, among others. Dahlen became known to a wide audience in 1978 in Michael Pfleghar's series "Klimbim". Together with Ingrid Steeger and Iris Berben, Dahlen also played in the series "Two Heavenly Daughters". In "A heart and a soul" he took over the role of the son-in-law of "Ekel Alfred" after Diether Krebs left. He also took part in television series such as “The Commissioner”, “The Men from K3”, “Coast Guard” or “Tatort”.