[1] Ahern attended St Augustine's College and represented Munster and Ireland at under-18 clubs level, winning an inter-provincial title with the former during the 2017–18 season.
[8] A shoulder injury sustained in the same month required surgery, ruling Ahern out until possibly March 2023.
[11][12] One month later, Ahern was selected in the Ireland under-20s squad for the 2019 World Rugby Under 20 Championship, his first call up at that level internationally.
[19] Though the remainder of the tournament was cancelled due to the COVID-19 pandemic, Ahern earned widespread praise for his performances.
[21] Ahern was selected in the Emerging Ireland squad that travelled to South Africa to participate in the Toyota Challenge against Currie Cup teams Free State Cheetahs, Griquas and Pumas in September–October 2022.