 He was educated at Belvedere College, Dublin, and University College Dublin, where he studied history, and the King's Inns.He was president of the Student Representative Council at UCD and Auditor of the Literary and Historical Society (UCD) and won The Irish Times National Debating Championship in 1973.Hardiman was married to Judge Yvonne Murphy, from County Donegal, a judge of the Circuit Court between 1998 and 2012, who conducted important inquiries relating to sex abuse including the Murphy Report and the Cloyne Report.