Born in Kilkenny, Larkin first played competitive hurling following encouragement from his father. He attended St. Kieran's College where he began his college hurling career as goalkeeper at under-14 level. Larkin simultaneously came to prominence with the James Stephens club at juvenile and underage levels, winning two county under-21 championship medals in 2000 and 2002. He subsequently joined the James Stephens senior team and was at centre-forward when the club won the All-Ireland title in 2005. Larkin also won two Leinster medals and three county senior championship medals. As a Gaelic footballer with James Stephens he also won two county senior championship medals.