Education
O'Mahony completed the 3-year Academy, but was released.
O'Mahony completed the 3-year Academy, but was released.
He plays club rugby for Clontarf FC.
At the conclusion of the 2011–12 season, O'Mahony was given a development contract in the senior squad. He made his full debut on 1 September 2012, as a replacement in 's opening 2012–13 Pro 12 league fixture against Edinburgh at Murrayfield. O'Mahony extended his development contract for a further year in early April 2013.
He made his first start for in a Pro 12 fixture against Cardiff Blues on 8 February 2014. He signed a one-year development contract extension in March 2014. In June 2015, it was announced that O'Mahony would be leaving.