He plays hurling with his local club Glenroe and with the Limerick senior inter-county team.
He was educated locally at Glenroe NS and went on to complete a law degree at Trinity College in the 1990s, playing both Sigerson and Fitzgibbon Cup.
O'Brien first came to prominence on the inter-county scene as a member of the Limerick intermediate hurling team.
As a result of this O'Brien joined the county senior team and made his debut in an Oireachtas game against Kilkenny in October 1998.
A victory over Cork in the Munster Championship in 2001 was Limerick's last provincial win until a defeat of Tipperary following a three-game saga in 2007.