He emigrated to the U.S. in 1914. He married a former model, Martha Tekla Sikorski, the daughter of Polish immigrants, and had one son, Rudy Flothow. His half-brother Wolfgang Hoeffer, a U.S. counterintelligence agent, was found shot to death in the immediate aftermath of Otto John's defection to East Germany.

His earliest involvement in the film industry was in distribution, joining Paramount in 1915. Flothow consistently worked with small budgets, with