McCarthy rejoined Connacht at the beginning of the 2007–08 season. He played in 14 games for the team in the 2007–08 Celtic League. McCarthy also started in all 6 of Connacht's group games in the 2007–08 European Challenge Cup, which included two matches against his former side Newcastle. The 2008–09 saw him make fewer appearances in both competitions, playing in just 9 of Connacht's 2008–09 Celtic League matches and four of their Challenge Cup games.