Competing as both a lightweight and a light welterweight Jim McCourt was regarded as one of the best Irish boxers of all-time, winning seven national titles. At the 1964 Tokyo Olympics McCourt won bronze in the lightweight class after a closely fought semi-final match against Vilikton Barannikov. Not long after the Olympics McCourt defeated Barannikov in a match in Dublin.
At the 1965 European Amateur Boxing Championships McCourt won a bronze medal again as a lightweight. The following year he moved up to the light-welterweight class where he won gold at the 1966 British Empire and Commonwealth Games for Northern Ireland with victory against Aaron Popoola of Ghana. McCourt returned to the Olympics for the 1968 Games in Mexico City, and while he did not replicate his earlier success he did have the honour of being the flagbearer for Ireland at the Opening Ceremony.