Dardis was born in New York City in 1926 to Michael Gregory and Josephine Coletta Dardis. Dardis married Jane Buckelew in 1947. The couple divorced in 1982. They had three children.
Dardis died of respiratory failure in New York in 2001.
From 1952 to 1955, Dardis worked as an associate editor at Avon Books. In 1955, Dardis became the executive director for the Berkley Publishing Corporation in New York City. He became editor-in-chief at that corporation in 1960 and held that position until 1972.