Hehn was first apprenticed to a baker, before switching to an acting career. On stage from 1929 and in supporting roles on screen, he was more often than not cast as uniformed army or air force officers. Beginning in the 1960's, Hehn enjoyed a successful resurgence on television, including a guest spot on the cult sci-fi series "Raumpatrouille - Die phantastischen Abenteuer des Raumschiffes Orion".