McCarthy is studying engineering at University College Dublin and plays for UCD in the All-Ireland League.
His father, Conor, was a scrum-half for Connacht, and his sister, Lisa, won a hockey scholarship in the United States, having represented Ireland at various age-grade levels.
[2] Having represented Leinster at under-16 and under-18 level, McCarthy joined the provinces sub-academy in 2013, before entering the full academy ahead of the 2014–15 season.
[4] During the following season, McCarthy again experienced domestic success, featuring off the bench during Leinster's 18–15 win against Glasgow Warriors in the final of the 2018–19 Pro14.
[5] McCarthy joined Leinster's provincial rivals Munster on a two-year contract after the completion of the 2018–19 season,[6] and made his competitive debut for the province in their opening 2019–20 Pro14 39–9 win against Welsh side Dragons on 28 September 2019.