Denis Colin Leary was born on August 18, 1957, in Worcester, Massachusetts, the son of Roman Catholic immigrant parents from County Kerry, Ireland. His mother, Nora (née Sullivan) (b. 1929), was a maid, and his father, John Leary (1924–1985), was an auto mechanic. Being the son of Irish parents, Leary is a citizen of both the United States and Ireland. Through marriage, Leary is a third cousin of talk show host, Conan O'Brien.