The son of the 13th Earl of Antrim, Hector McDonnell was brought up at Glenarm Castle and educated at Eton and Oxford. He studied art in Munich and Vienna 1965-66. He has travelled extensively and worked in Africa, Asia and the United States.

The underlying subject matter of all his work is a concern for people, places, local habits and ways of life. In 1983 the Ulster Museum purchased his painting Bewley's Restaurant 11 (1980). He has been a regular contributor to the RUA since 1985.