McCarthy was called up for the 2012 November international matches. McCarthy played in each game, starting both full tests that Ireland played. He partnered Donnacha Ryan in the second row in the match against South Africa on 10 November, as well as the game with Argentina on 24 November. Two months later he was called up to the 2013 Six Nations squad. This championship saw McCarthy start 4 of Ireland's 5 games, missing the Scotland game through injury.