Career
At the 1924 Olympics Games he scored the Ireland (FAI)"s first ever goal in a senior international. During his career Duncan was known by the nickname Dirty Duncan. Together with Charlie Dowdall, Thomas Murphy, Ernest McKay and Michael Farrell, Duncan was one of five players from Street James"s Gate, included in the Irish Free State squad for the 1924 Olympics Games.
In 1924 Duncan made 4 appearances and scored 2 goals for the Irish Free State.
The first two of these games were played at the 1924 Olympics Games. On 2 June Duncan also played in this game against the Netherlands but the Irish Free State lost 2-1 after extra-time.
In March 1926 he travelled as a reserve with the Irish squad to play Italy, but did not play.