Patrick O'Neill was born in Toronto, Ontario in 1940. He married Mora Dianne O'Neill in 1967 and had two sons, St. John and Brendan. O'Neill obtained a Bachelor of Arts in History from St. Jerome's College, University of Waterloo in 1967, a Master of Arts in Theatre from the University of South Dakota in 1969, and a Ph.D. in Theatre from Louisiana State University in 1973.

O'Neill was a leading scholar in Canadian theatre history and published extensively. In 1995 he received the Richard Plant Essay Prize from the Association for Canadian Theatre Research. In 2002 he received an Award for Research Excellence from Mount Saint Vincent University. In 2004 he received a Fulbright Research Fellowship, awarded by The Department of State, Washington.

O'Neill worked as an Assistant Professor (1972-1975) at the University of Saskatchewan in Saskatoon, Saskatchewan and as an Assistant Professor (1975-1980), Associate Professor (1980-1993), and Professor (1993-2006) at Mount Saint Vincent University in Halifax, Nova Scotia. He also worked as a Visiting Fellow (1982-1983) at Royal Holloway College, at the University of London, and as an Associate Professor, Part-time (1987-1991) at Dalhousie University in Halifax, Nova Scotia.

During his time at Mount Saint Vincent University O'Neill served in numerous positions, including Director of Research and International Liaison Officer (2002-2004), Coordinator, Speech and Drama (1975-2002), and as a member of the University Senate (2002). O'Neill also served on numerous committees, including the University's Tribute Committee (1999-2006), University Review Committee (1998-1999), and the Exceptional Service Awards Committee (1998-2006). Patrick O'Neill was also involved with various drama presentations. In addition to his work at the University, O'Neill served as a member of the Nova Scotia Innovation Trust (2002-2004), as a member of the Nova Scotia Health Research Foundation (2002-2004), as a Maritime Representative (1998-2000) and Treasurer (1982-1984) for the Association for Canadian Theatre Research, and as a member of the Social Sciences and Humanities Research Council (SSHRC) Research Committee for Architecture, Fine Arts, Drama (1993-1995). O'Neill also served as a parliamentarian for the Registered Nurses Association of Nova Scotia (1984-1998) and the Association of Professional Engineers of Nova Scotia (1996), as well as an External Reviewer for SSHRC applications (various years) and as an External Examiner for a University of Toronto Ph.D. thesis, a McGill University M.A. thesis, and a University of Saskatchewan M.A. thesis. O'Neill died in Ireland in 2006.