Born in Celbridge, County Kildare, Mackey first arrived on the inter-county scene when he first linked up with the Kildare minor team, before later lining out with the under-21 side. He made his senior debut in the 2008 Christy Ring Cup. Ó Muineacháin has gone on to play a key role for Kildare since then, and has won one Christy Ring Cup medal and one National League (Division 3A) medal.
