Minor and under-21

Mulcahy first played for Limerick at minor level. He made his first appearance for the team on 23 June 2007 in a 3-21 to 0-12 defeat by Tipperary in the Munster Championship.^[6] Mulcahy was eligible for the minor grade again in 2008, however, Limerick's season ended with a 0-23 to 0-11 defeat by Cork.

Mulcahy subsequently joined the Limerick under-21 hurling team. On 3 August 2011, he scored 2-01 from play when Limerick defeated Cork by 4-20 to 1-27 in the final of the Munster Championship.^[7]

Senior

On 15 February 2009, Mulcahy made his senior debut as a substitute in a National League defeat by Kilkenny at Nowlan Park.^[8] Later that season he made his first championship appearance in a 0-25 to 0-17 defeat by Waterford in the Munster Championship.^[9]

Mulcahy claimed his first silverware at senior level on 30 April 2011 when Limerick won the National League Division 2 title after a 4-12 to 2-13 defeat of Clare in the final at Cusack Park.^[10]

On 14 July 2013, Mulcahy was at right corner-forward in Limerick's 0-24 to 0-15 defeat of Cork in the Munster final.^[11] He ended the season by being nominated for an All-Star award.^[12]

On 19 August 2018, Mulcahy scored 1-02 from play when Limerick won their first All-Ireland title in 45 years after a 3-16 to 2-18 defeat of Galway in the final.^[13] Later that day he was named on The Sunday Game Team of the Year.^[14] Mulcahy ended the season by winning an All-Star Award.^[15][16]

On 31 March 2019, Mulcahy was selected at left corner-forward for Limerick's National League final meeting with Waterford at Croke Park. He collected a winners' medal after scoring three points from play in the 1-24 to 0-19 victory.^[17] On 30 June 2019, Mulcahy won his first Munster Championship medal in six years after scoring two points from full-forward in Limerick's 2-26 to 2-14 defeat of Tipperary in the final.^[18] He ended the year by receiving his second successive All-Star nomination.^[19]