He was born in the West of Ireland and is a graduate of the Institute of Art, Design and Technology in Dun Laoghaire, Dublin. He holds a Masters in Fine Art Photography from The University of Ulster, Belfast. O Halloran's work has appeared in magazines such as The New York Times Magazine, The Sunday Times Magazine, Stern, Le Monde, TIME, GEO, The Financial Times Magazine and Cosmopolitan Magazine. His work has been recognized by World Press, American Photography, Alliance Francaise, and the Taylor Wessing Portrait Prize. He is also a winner of the Terry O'Neill Photography award.