He was educated at University College Dublin and St Patrick's College of Education, Drumcondra, he worked as a teacher at primary and secondary level in Dublin, Offaly and Kerry before taking over his family's menswear business in Listowel.
He was a cousin of Kit Ahern, who served as a Teachta Dála (TD) and senator. In December 2008, he sent silk ties (worth €25 each) to approximately 400 County councillors. He is the Fianna Fáil Seanad spokesperson on Transport, Tourism and Sport.
O'Sullivan admitted making "around a dozen" calls and texts to support Healy-Rae after being asked to do so by Healy-Rae's campaign manager.
He was a member of Listowel Town Council from 1985 to 2007 and Kerry County Council from 1991 to 2007.
