He earned his 100th cap for Ireland against England on 27 February 2010. He was the first Irish player to do so. Hayes lead Ireland out onto the pitch before the game to a standing ovation from the Twickenham crowd. Ireland went on to win the game 20–16 with a late try by Tommy Bowe. Hayes did not play against the Barbarians in Ireland's first match of the Summer Tests, and missed the Test against New Zealand through illness. He came on as a replacement against New Zealand Maori but was left out of the squad to play Australia, thereby losing his title of Ireland's most capped player to Brian O'Driscoll.