Born in Feodosia, in the Crimea, Russia, Vallin came to the United States at age three with his South American mother, Mrs. Nardine Thomes, on the S/S Muskegon, which arrived at the Port of Boston on May 6, 1922.

In 1942, he joined the Pasadena Playhouse, and received his first co-star billing in the film The Panther's Claw together with Sidney Blackmer, and showed promise in Secrets of a Co-Ed with Otto Kruger.

Vallin's fortunes improved in 1943 when he was hired as the villain in the East Side Kids comedy Clancy Street Boys.

[citation needed] Vallin worked steadily in many of Katzman's features and serials, playing a variety of character roles: streetwise reporters, sinister villains, heroic internationals, and savage natives.

[citation needed] Occasionally he showed up in such television series as Brave Eagle, Sheriff of Cochise, Bat Masterson, Jefferson Drum, The Adventures of Wild Bill Hickok, The Lone Ranger and Wyatt Earp.