Paddy Duffy made his Olympic debut at the 1948 London Games and went on to become the most influential figure in Irish fencing during the 1950s and 1960s - establishing the Salle Duffy and coaching generations of Irish fencers who would build the sport into a far stronger position than it occupied in London. He was selected for the 1952 Helsinki Olympics by the OCI on a 7-6 vote, and despite the turbulent circumstances in which the Irish fencing team made their way to Finland and were initially refused entry to the Irish quarters in the Olympic Village, he competed in both foil and epee there - recording two victories in the foil.
A member of the St. Vincent's GAA club, Duffy was a keen sportsman and played hurling and Gaelic football for them. He learned to fence during his time in the Irish Army during the Irish Emergency (1939-48), and in 1946 took up the sport competitively, Between 1947-52 he won Irish titles in the épée, sabre and all-weapons categories every year. Duffy later turned professional and ran the Salle Duffy in Dublin, where he coached many young fencers as it gained a reputation for being one of the leading fencing clubs in Ireland. At the time of his death, Duffy was the only professional fencer in Ireland. His brother Vincent was also an Irish foil champion.