McCarthy first came to prominence on the inter-county scene as a member of the Cork minor hurling team when he was just sixteen years-old in 1998. In his debut season he failed to make the starting fifteen, however, he came on as a substitute in the Munster final. Clare were the opponents on this occasion but they were no match for Cork. A 3-13 to 0-8 score line gave Cork the victory and gave McCarthy a Munster winners' medal. The subsequent All-Ireland final saw Cork take on Kilkenny. McCarthy came on as a substitute once again as 'The Rebels' beat their rivals. A 2-15 to 1-9 score line gave Cork the win and gave McCarthy an All-Ireland minor winners' medal.