Alioto was born in San Francisco in 1916. His father was a Sicilian immigrant who owned and operated several fish processing companies. His mother, Domenica Mae Lazio, was born in San Francisco in 1893. His parents met on a fishing boat while escaping the 1906 San Francisco earthquake. Alioto's father was reportedly the brother of Milwaukee crime family boss John Alioto. Alioto attended Sacred Heart High School. he graduated with honors from St. Mary's College in Moraga, California in 1937 and from law school at The Catholic University of America with honors, in Washington, D.C. in 1940.