Along with his parents, John and Rose Anna Moore, brothers Tom, Matt, and Joe, and sister Mary, he emigrated to the United States as a steerage passenger on board the S.S. Anchoria.

While working at D. W. Griffith's Biograph Studios, Moore met a young Canadian actress named Gladys Smith, whom he married on January 7, 1911.

This humiliation, together with his wife's meteoric rise to fame, drastically affected Moore, and alcohol became a problem that led to violent behavior and his physically abusing Pickford.

He was a popular star at Selznick Pictures along with Olive Thomas, Elaine Hammerstein, Eugene O'Brien and Conway Tearle.

He competed, as the third lead, with Cary Grant and Noah Beery, Sr. for the attentions of Mae West in She Done Him Wrong, Paramount's most lucrative film of 1933.