He was educated locally at St. John's De La Salle, a school associated with the O'Loughlin Gaels hurling club.
In 1971 he won his first Leinster title, however, in spite of an outstanding display by Eddie Keher, Kilkenny lost to Tipperary in the All-Ireland final.
In 1972 he won a second Leinster title before helping Kilkenny to defeat Cork in the subsequent final to win his first All-Ireland medal.
1973 saw O'Brien win another Leinster medal, however, Kilkenny were defeated by Limerick in the All-Ireland final.
In 1976 O'Brien helped Kilkenny to a National Hurling League title, however, the side later lost their provincial crown to Wexford.