a member of the Cork senior hurling team. Playing career Midleton CBS During his secondary schooling at Midleton CBS Secondary School, O'Sullivan was more renowned as a Gaelic footballer before joining the college's senior hurling team. On 26 March 1995, he was at right wing-forward on the Midleton CBS team that defeated Lismore CBS by 3-18 to 3-05 to win the Harty Cup title. O'Sullivan lined out on the Midleton CBS senior hurling team for a further two years. He later said: "I found Harty hurling much tougher than minor inter-county. The games were of an intensity that I had never previously encountered. You became aware very quickly of the standard required to compete and you had to adapt to the various styles played by schools from the different counties. It toughened me up a fair bit and stood to me in my later career with Cork." Cloyne O'Sullivan joined the Cloyne club as a seven-year-old and played in all grades at juvenile and underage levels. Speaking of his first hurling appearance he said: "I went on not knowing what I was leaving myself in for but I knew when I came off I wanted more of it." O'Sullivan was first selected for the club's intermediate team in 1995. On 20 October 1996, O'Sullivan was at left wing-back when Cloyne drew with Newtownshandrum in the final of the Cork Intermediate Championship. He lined out in the same position a fortnight later when Cloyne were defeated in the replay by 0-12 to 0-09. O'Sullivan lined out at left wing-back in his second successive final on 2 November 1997. A 1-12 to 1-07 defeat of Delanys secured the title and a Cork Intermediate Championship medal for O'Sullivan. On 31 October 2004, O'Sullivan was at right wing-back when Cloyne qualified to face Na Piarsaigh in the final of the Cork Senior Championship. He was switched to centre-back during the game and scored a point from as free, however, Cloyne were defeated by 0-17 to 0-10. Cloyne qualified for a second successive Cork Senior Championship final with Newtownshandrum providing the opposition on 16 October 2005. O'Sullivan lined out at centre-back in the 0-15 to 0-09 defeat. O'Sullivan was appointed captain of the Cloyne team for the 2006 championship, while he also took up a new position at centre-forward. On 22 October 2006, he captained the team when they were defeated by 2-19 to 3-14