On 16 April 1993, O'Neill made his first appearance for the Limerick under-21 team. He scored 2-01 from play in the 5-09 to 4-08 defeat of Waterford in the Munster Championship. On 23 July 1993, O'Neill scored a goal when Limerick suffered a 1-18 to 3-09 defeat by Cork in the Munster final.
