Born in Blackpool, Cork, Mulcahy first played competitive Gaelic games during his schooling at the North Monastery. He arrived on the inter-county scene at the age of seventeen when he first linked up with the Cork minor teams as a dual player before later joining the under-21 sides. He made his senior hurling debut during the 1983 championship. Mulcahy immediately became a regular member of the starting fifteen and won three All-Ireland medals, five Munster medals and one National Hurling League medal. The All-Ireland-winning captain of 1990, he was an All-Ireland runner-up on two occasions.