In May 2010, Tuohy was named in the 33-man squad for Ireland's summer tour to New Zealand and Australia. He went on to play for Ireland in the non-cap match against the Barbarians on 4 June 2010. On 12 June 2010, Tuohy made his test debut, coming on in the first half of the game against New Zealand in New Plymouth. Ireland lost the game by 66–28, with Tuohy scoring a try in the first minute after coming on. In 2014, Tuohy was called up to replace Paul O' Connell in Ireland's home six nations game against Scotland. He played a pivotal role in Ireland's victory over the Scots and retained his position on the bench for Ireland's next home game against Wales. His appearance as a substitute in that game was cruelly cut short with a broken forearm.