Born in Tullaroan, County Kilkenny, Walsh first played competitive hurling during his schooling at St. Kieran's College. He arrived on the inter-county scene at the age of seventeen when he first linked up with the Kilkenny minor team, before later joining the under-21 side. He joined the senior panel during the 2002 championship. Walsh became a regular member of the starting fifteen the following year, and won nine All-Ireland medals (two as a non-playing substitute), ten Leinster medals and seven National League medals. He was an All-Ireland runner-up on two occasions.