Father de Souza studied economics and political studies (BA Hons.) and public policy (MPA) at Queen's University before doing graduate study in development economics (MPhil) at the University of Cambridge in England. His seminary formation was completed at St. Philip's Seminary in Toronto (Bachelor of Thomistic Thought) and at the Pontifical North American College in Rome (STB, Pontifical Gregorian University; STL, Pontifical University of the Holy Cross). 

Father Raymond J. de Souza was ordained a Catholic priest on 20 July 2002 for the Archdiocese of Kingston, Ontario. He currently serves as chaplain of Newman House, the Catholic chaplaincy at Queen's University, and as the pastor of Sacred Heart of Mary Parish on Wolfe Island, where he lives.

Besides teaching in Economics, Father de Souza teaches in the Faculty of Education and is a Senior Fellow of Massey College at the University of Toronto. He is a Senior Fellow at Cardus, Canada's leading Christian think tank, and serves on the board of directors of Catholic Christian Outreach and the Centre for Israel and Jewish Affairs. In 2014 he was appointed Chair of the Advisory Council to the Office of Religious Freedom in the Canadian foreign affairs department, and from 2011 to 2014 he served as a consultant to the religious liberty committee of the United States Conference of Catholic Bishops.

Father de Souza writes regular columns for several publications including the National Post.  Since co-founding it in 2011, he has been editor-in-chief of Convivium, an online Canadian magazine about faith in our common life.