Alda, an American of Italian descent, was born Alphonso Giuseppe Giovanni Roberto D’Abruzzo in New York, New York, the son of Frances (née Tumillo) and Antonio D’Abruzzo, a barber born in Sant’Agata de’ Goti, Benevento, Campania, Italy. He graduated from Stuyvesant High School in New York in 1930. He began as a singer and dancer in vaudeville after winning a talent contest, and moved on to burlesque.

Alda is known for portraying George Gershwin in the biopic Rhapsody in Blue (1945) as well as the talent agent in the Douglas Sirk classic Imitation of Life (1959). He was very successful on Broadway, starring in Guys and Dolls (1950), for which he won a Tony Award, and in What Makes Sammy Run? (1964). He was also the host of the short-lived DuMont TV version of the game show What’s Your Bid? (May–June 1953).

Alda’s first wife, and mother of actor Alan Alda, Joan Browne, was a homemaker and former beauty pageant winner. Alda was married to his second wife, Flora Marino, an Italian actress whom he met in Rome, until his death.  Alda made two guest appearances with his son Alan on M*A*S*H, in the episodes “The Consultant” (January 1975) and “Lend a Hand” (February 1980). The latter episode also featured Antony Alda (1956–2009), his youngest son by his second wife.  Alda died on May 3, 1986, aged 72, after a long illness following a stroke.