O'Brien first played Gaelic football and hurling in the Lough Leagues, before later lining out as a schoolboy with Sullivan's Quay CBS.
O'Brien was still in his teens when he lined out with the intermediate team before making his senior debut as a dual player.
O'Brien has his first senior successes as a hurler when St. Finbarr's claimed the Cork, Munster and All-Ireland titles during the 1974–75 season.
[2] O'Brien became only the second player since John Lyons to captain his club to hurling football honours.
O'Brien first appeared on the inter-county with Cork as goalkeeper on the minor team that beat Derry in the 1969 All-Ireland MFC final.