In 1911, however, he finished his cadet hood and moved to Berlin in 1912 where he created the "Art Film Publishing House Company" and made, as a director, screenwriter and producer, his first feature Black Blood (1912) with Curt Goetz in the lead role.

In 1930 he directed the comedy Him or Me (1930), and many successful adventure films were to follow, such as Shade of the Underworld (1931), Johnny Steals Europe (1932), The Ship Without a Port, The Call of the Jungle (1935) and His Best Friend (1937).

At the film's climax, an air-raid on a German city frees the zoo animals from their cages; when they run loose in the streets, the people are terrified and only the heroic trapper can recapture the beasts.

During World War II, this film was suppressed by Reich censors who did not want the German people to believe that Germany was in danger from aerial bombardments.

After the collapse of the Third Reich, Harry Piel, who had been a sustaining member of the SS, and had at first concealed this, was sentenced to six months detention and five years professional disqualification.