He had a strong interest in the fledgling motion picture industry, and when Essanay Studios offered him the opportunity to become a scriptwriter, he took the job.

[1] At that time, some of the East Coast movie makers began to spend winters in California where the climate allowed them to continue productions requiring warm weather.

Dwan managed to track the company down, and learned that they were waiting for a film director (who was an alcoholic) to return from a binge and allow them to resume their work.

After making a series of westerns and comedies, Dwan directed fellow Canadian-American Mary Pickford in several very successful movies as well as her husband, Douglas Fairbanks, notably in the acclaimed 1922 Robin Hood.

Over a long career spanning almost 50 years, Dwan directed 125 motion pictures, some of which were highly acclaimed, such as the 1949 box office hit, Sands of Iwo Jima.

Daniel Eagan of Film Journal International described Dwan as one of the early pioneers of cinema, stating that his style "is so basic as to seem invisible, but he treats his characters with uncommon sympathy and compassion.