He was selected in goal the following year on Tipperary's inaugural under-21 team and ended the campaign with a winners' medal after an 8-09 to 3-01 defeat of Wexford in the 1964 All-Ireland under-21 final.
He earned a recall to the senior team in 1970 and came established himself as first-choice goalkeeper after coming on as a substitute for John O'Donoghue in the 1970 Munster final.
[11] O'Sullivan's inter-county career ended in November 1972 when he received severe burns to his hands and face in a workplace accident.
[13] O'Sullivan enjoyed his first coaching success when he was part of the Seán Treacy's management team when the club won the West Tipperary SHC title in 1982.
[14][15] O'Sullivan returned to club management with Cashel King Cormacs in 1988 and helped guide the team to the West Tipperary SHC title that year.