Duff was ever-present on the wings for Ireland in their UEFA Euro 2012 qualifying campaign and he was part of the team that secured qualification for UEFA Euro 2012 with an unprecedented 5–1 aggregate play-off win over Estonia. He was named in Trapattoni's 23-man squad for the 2012 European Championships in Poland and Ukraine and was given the number 11 jersey. He captained Ireland on his 100th cap against Italy in Ireland's final group game of the tournament, and Duff's own final match for Ireland, on 18 June 2012.