Kearney was added to the Waterford senior team in advance of the 2015 National League. He made his first appearance on 14 February 2015 when he lined out at left corner-forward in a 0-22 to 2-16 draw with Limerick. On 3 May 2015, Kearney won a National League medal as a non-playing substitute when Waterford defeated Cork by 1-24 to 0-17 in the final. He was later included on the Waterford panel for the Munster Championship. On 12 July 2015, Kearney was an unused substitute when Waterford were beaten for the fourth time in six seasons by Tipperary in the Munster final. On 1 May 2016, Kearney was an unused substitute when Waterford drew 0-22 apiece with Clare in the National League final. He also remained on the bench for the replay, which Waterford lost by 1-23 to 2-19. On 10 July 2016, Kearney was an unused substitute when Waterford suffered a 5-19 to 0-13 defeat by Tipperary in the Munster final. On 3 September 2017, Kearney was selected as a substitute when Waterford faced Galway in the All-Ireland final. He remained on the bench and ended the game as a runner-up following Galway's 0-26 to 2-17 victory. On 3 June 2018, Kearney made his first appearance in the Munster Championship when he lined out at right corner-forward against Tipperary. He was substituted in the 47th minute in the eventual 2-22 apiece draw. On 31 March 2019, Kearney was named at centre-forward but lined out at right wing-forward when Waterford faced Limerick in the National League final. He was held scoreless in the 1-24 to 0-19 defeat.