Born near Saint John, New Brunswick, he began his career by studying at the New England Conservatory of Music in Boston. He made several silent movies in the 1920s, then made some early talkie musicals, then played second fiddle to the main male star in such films as Saratoga and The Girl of the Golden West. It wasn't until he starred in How Green Was My Valley that he became well-known.
He starred opposite Greer Garson in Blossom in the Dust and in Mrs. Miniver (for which he was nominated for the Academy Award for Best Actor). He was nominated again in 1944 for Madame Curie, but he left Hollywood in the mid-1950s for the stage. He retired fully in 1971, and died in Santa Monica, California.
Pidgeon has a star on the Hollywood Walk of Fame at 6414 Hollywood Blvd.