Harry Behn was born in 1898 in McCabe, Arizona, which is now a ghost town, in Yavapai County in what was then the territory of Arizona. He was the son of Henry K. Behn, and immigrant from Germany, and Maren (or Marion) Christensen Behn, an immigrant from Denmark.

At the age of 18, after he had been accepted as a student at Stanford University but before he went there, he met Henry Berger, a photographer affiliated with the Prizma Company, who hired Harry Behn as his assistant for the summer. The two of them went to Yellowstone and Glacier National Park, where they were supposed to take a series of nature slides for Prizma. A family emergency took Henry Berger away for a month, and during this time Harry Behn stayed in Glacier National Park with all the photographic equipment, waiting for Berger to return. While Berger was gone, Harry Behn made friends with some young Blackfoot Indians whose reservation was in the park, and lived with them. He was invited to join the tribe, and underwent all the tests and rituals involved in becoming a Blackfoot, and received the name Big Wolf Medicine. For a while he was actually listed as a Blackfoot with the Indian Service, making him eligible for oil royalties being paid to the Blackfoot tribe, and he actually received a check, but he later convinced the Indian Service to give the money to the tribe.

He received his education at Stanford University, which he attended in 1918, and Harvard University (S.B., 1922).

Harry Behn was involved in writing the screenplay for a number of films, including the 1930 war film Hell's Angels that was directed by Howard Hughes.

In the mid-1930s, Harry Behn joined the faculty of the University of Arizona, where he was a professor of English and ran the educational radio programs. He founded and edited the Arizona Quarterly, and also founded the Phoenix Little Theater in the 1920s, and the University of Arizona Press in 1960.

Harry Behn wrote many children's books, and also translated Japanese haiku, with the help of people who knew this language.

Harry Behn also produced a number of paintings, although he is not as well known as an artist as he is as a writer. Some of his paintings are owned by his descendants.

Harry Behn was married to Alice Lawrence (1905—1989), and had two sons Prescott Behn and Peter Behn, and one daughter Pamela Behn.He died in Seville, Spain, while traveling there; his place of residence at the time of his death was Greenwich, Connecticut. He was 74 years old when he died.