Born Joseph Goucher on December 11, 1889, he was the 14th of 17 children born to a father of French-Canadian descent and a mother of Irish descent in Woonsocket, Rhode Island. His middle name was either "Narcisse" or "Nelson" (varying sources). He took his professional surname from the maiden name of his mother, Bridget Mary Dowling, who was born in Smithfield, Rhode Island. His father was Charles Goucher who was born in St Marcel, Province of Québec, Canada.
He appeared on stage for many years, including appearances in the Ziegfeld Follies. His most famous role was as "Tom Wingfield" in the original Broadway production of The Glass Menagerie, starring opposite Laurette Taylor and Julie Haydon. He produced the play's original Chicago production in 1944, and followed it to Broadway.
Dowling sought the 1934 Democratic nomination for the United States Senate seat from Rhode Island. At the time, TIME magazine reported that his great-grandfather and two great-grand uncles were the founders of Goucher College for Women in Baltimore, and that "he was the 14th in a family of 17 children; his schooling had extended only up to the third grade; he had been a cabin boy and a music hall singer ... and he owned a sausage factory in California."
He was married to the Glasgow, Scotland-born actress and stage performer, Rachel Rice Dooley (October 30, 1888 — January 28, 1984) who specialized in physical comedy; they had two children, Jack and Maxine. Jack Dowling died serving in the World War II.
- Date and year of birth as per baptismal records of Precious Blood church, Woonsocket, Rhode Island, where Dowling was christened
- Cullen, Frank and Hackman, Florence (2006). Vaudeville, Old and New: An Encyclopedia of Variety Performers in America, pp. 322-23. Routledge. ISBN 0-415-93853-8.
- Time magazine description of Dowling