O'Brien's skill was recognised at an early age when he won a South Limerick school's medal with Bruree National School, before an unrewarding spell at Rathluirc CBS. His career at club level with Bruree spanned three decades.
O'Brien won a Munster Championship medal with the Limerick minor hurling team in 1963, before being subsequently selected for the Limerick under-21 and junior teams. He made his first appearance for the Limerick senior hurling team during the 1966-67 National League and enjoyed his greatest successes as a defender over the following decade. In 1973 O'Brien became the first Bruree clubman to win an All-Ireland Championship medal, having earlier won Munster Championship and National Hurling League titles.
