William Frawley was born in Burlington, Iowa. As a boy he sang at St. Pauls' Catholic Church and played at the Burlington Opera House. His first job was as a stenographer for the Union Pacific Railroad. He did vaudeville with his brother Paul, then joined pianist Franz Rath in an act they took to San Francisco. After four years, in 1914 he formed a light comedy act with his new wife Edna Louise Broedt, "Frawley and Louise," touring the Orpheum and Keith circuits until they divorced in 1927.
His Fred Mertz role lasted until the show ended in 1960 after which he did a five year stint on "My Three Sons." Poor health forced his retirement. His final on-camera performance was on October 25, 1965 with a brief cameo appearance in Lucille Ball's second television sitcom The Lucy Show with Frawley playing a horse trainer and Lucy commenting, "He reminds me of someone I used to know."
He collapsed of a heart attack on March 3, 1966, aged seventy-nine, walking along Hollywood Boulevard after seeing a movie. He is buried in San Fernando Mission Cemetary in Los Angeles, California.