Born in Waterford, Grimes first played competitive hurling during his schooling at Mount Sion CBS. He arrived on the inter-county scene at the age of 17 when he first linked up with the Waterford minor team. He joined the senior team during the 1947-48 league. Grimes immediately became a regular member of the starting 15, and won two All-Ireland medals, three Munster medals and one National Hurling League medal on the field of play. He was an All-Ireland runner-up on two occasions.