O'Halloran was born in Philadelphia, and was raised by his mother, Mary, and stepfather, Peter Paul Patrick O'Halloran; in his book "Family Legacy", he claims to be the illegitimate son of mafia hitman Albert Anastasia. He lived in Runnemede, New Jersey. Fighting as "Irish" Jack O'Halloran from Boston, he was a heavyweight boxing contender active from 1966 to 1974. The 6-foot, 5-inch O'Halloran was undefeated in his first 16 professional fights.