2–10 defeat by Na Piarsaigh. Mahony won a seventh Waterford Senior Championship title on 7 October 2018 when Ballygunner defeated Abbeyside by 2–19 to 0–13 to secure a fifth successive title. He was again at centre-back on 18 November 2018 when Ballygunner defeated Na Piarsaigh by 2–14 to 2–08 to win the Munster Club Championship. Mahony ended the season by being chosen on the Club Team of the Year. On 13 October 2019, Mahony lined out at centre-back when Ballygunner faced De La Salle in the final. He collected an eighth winners' medal overall following the 1–24 to 1–15 victory. Waterford Minor and under-21 Mahony first played for Waterford as a member of the minor team during the 2008 Munster Championship. He made his first appearance for the team on 25 June 2008 when he lined out at centre-back in a 4–13 to 1–06 defeat by Cork. Eligible for the minor grade once again the following year, Mahony once again lined out at centre-back when Waterford faced Tipperary in the Munster final on 12 July 2009. He ended the game with a winners' medal after the 0–18 to 1–13 victory. Mahony was still a member of the Waterford minor team when he was drafted onto the under-21 team in advance of the 2009 Munster Championship. He made his first appearance for the team on 15 July 2009 when he lined out at right wing-back in a 3–21 to 2–14 defeat of Tipperary. Mahony was again at right wing-back on 29 July 2009 when Waterford suffered a 2–17 to 2–12 defeat by Clare in the Munster final. He spent a further three seasons with the Waterford under-21 team but ended his underage career without any further success. Senior Mahony was drafted onto the Waterford senior panel during the 2010 Munster Championship. On 17 July 2010, he won a Munster Championship medal as a member of the extended panel following Waterford's 1–16 to 1–13 defeat of Cork in the final. On 13 February 2011, Mahony made his first appearance for the Waterford senior team when he lined out at midfield in Waterford's 3–16 to 2–19 draw with Dublin in the National Hurling League. On 10 July 2011, he was an unused substitute when Waterford suffered a 7–19 to 0–19 defeat by Tipperary in the Munster final. Mahony lined out in his first Munster final on 15 July 2012 when he was selected