Carmel Heaney was born in Dublin on the 21st July, 1924, the eldest child of Rosanna and Timothy O'Leary. She was educated at the Holy Faith convent, Glasnevin and at University College Dublin from which she graduated with an M.A. in History. After some years as a junior Civil Servant and in radio programming, she entered the Department of External Affairs (later the Department of Foreign Affairs). Her foreign postings were in San Francisco, Geneva and Boston where she was Consul General. She was a delegate to several sessions of the General Assembly of the United Nations in the 1970s. 

In 1970 Carmel married Henry Heaney, a Boston architect. She retired in 1989 and lives in Dublin. She leads a weekly philosophical discussion group, The Colloquy, and is an occasional contributor to the Irish Times.