 In the 2013–14 UEFA Europa League first qualifying round, O'Brien scored his first goal for the Saints on his 70th appearance when he scored the equaliser in the first leg against VMFD Žalgiris to make it 2–2 in the LFF Stadium in Vilnius, Lithuania.O'Brien represented the Republic of Ireland U23s in the 2007–09 International Challenge Trophy, playing in all three games.He won his first cap against Slovakia on 13 November 2007 and then earned a second cap in May 2008 against Northern Ireland.