Minor and under-21

Buckley first played for Kilkenny in 2009 when he joined the minor side. He won his first Leinster medal that year following Kilkenny's 1-19 to 0-11 trouncing of Wexford in the provincial decider. Galway provided the opposition in the subsequent All-Ireland decider on 6 September 2009. A devastating second quarter display was pivotal in powering the Westerners to a 2-15 to 2-11 victory.^[6]

In 2010 Buckley was appointed captain of the Kilkenny minor team. He won a second Leinster medal that year following a 1-20 to 0-10 trouncing of Dublin.^[7] The subsequent All-Ireland decider on 5 September 2010 pitted Kilkenny against Clare. "The Cats" were made to work hard before securing a narrow 2-10 to 0-14 victory, giving Buckley an All-Ireland Minor Hurling Championship medal and the honour of lifting the cup as captain.^[8]

Two years later Buckley was a key member of the Kilkenny under-21 team. He won his sole Leinster medal that year following a 4-24 to 1-13 trouncing of Laois.^[9] Kilkenny later faced Clare in the All-Ireland decider on 15 September 2012. A powerful second-half display, in which they outscored Kilkenny by 1-10 to 0-4, saw Clare take their second ever All-Ireland title in the grade.^[10]

Senior

Buckley made his senior debut for Kilkenny on 12 February 2012 in the final of the pre-season Walsh Cup. He came on as a substitute as Kilkenny defeated Galway to take the title by 2-20 to 1-14.^[11] Buckley was a regular during the subsequent league campaign which eventually saw Kilkenny faced old rivals Cork in the decider. A huge 3-21 to 0-16 victory gave him a first National Hurling League medal.^[12] Kilkenny were later shocked by Galway in the Leinster decider, losing by 2–21 to 2–11, however, both sides subsequently met in the All-Ireland decider on 9 September 2012.^[13] Kilkenny had led going into the final stretch, however, Joe Canning struck a stoppage time equaliser to level the game at 2–13 to 0–19 and send the final to a replay for the first time since 1959.^[14] The replay took place three weeks later on 30 September 2012. Galway stunned the reigning champions with two first-half goals, however, Kilkenny's championship debutant Walter Walsh gave a man of the match performance, claiming a 1–3 haul. The 3–22 to 3–11 Kilkenny victory gave Buckley a first All-Ireland medal.^[15]

Kilkenny's dominance showed no sign of abating in 2013, with Buckley winning a second successive league medal following a 2–17 to 0–20 defeat of Tipperary in the decider.^[16]

In 2014 Buckley collected his third successive league medal, as Kilkenny secured a narrow one-point 2–25 to 1–27 extra-time victory over Tipperary.^[17] Buckley subsequently secured his first Leinster medal, as a dominant Kilkenny display gave "The Cats" a 0–14 to 1–9 defeat of Dublin.^[18] On 7 September 2014 Kilkenny faced Tipperary in the All-Ireland decider. In what some consider to be the greatest game of all time, the sides were level when Tipperary were awarded a controversial free. John O'Dwyer had the chance to win the game, however, his late free drifted wide resulting in a draw.^[19] The replay on 27 September 2014 was also a close affair. Goals from brothers Richie and John Power inspired Kilkenny to a 2–17 to 2–14 victory.^[20] It was Buckley's second All-Ireland medal, while he was later presented with an All-Star.

Buckley won a second successive Leinster medal in 2015 following a 1-25 to 2-15 defeat of Galway in the provincial decider.^[21] Kilkenny subsequently defeated Galway in the All-Ireland final, earning Cillian his third Celtic Cross.^{[citation needed]}

Buckley scored the winning goal at the last minute of stoppage time to win Kilkenny's fourth consecutive Leinster title against Galway in 2023.