Cardinal Thomas Christopher Collins was born and raised in Guelph, Ontario, where his father was the circulation manager of the Guelph Mercury and his mother was a legal secretary. He is the only son and the youngest of three siblings. His childhood home was situated behind The Church of Our Lady, where he attended and served morning Mass.
Cardinal Collins considered being a teacher or a lawyer but was profoundly inspired by his Grade 11 English teacher, Father Newstead, at Bishop Macdonell Catholic High School, who knowing him, suggested that he should consider the priesthood. In 1969 he obtained a Bachelor of Arts (English) from St. Jerome College in Waterloo. In 1973 he obtained two degrees, a M.A. (English) from the University of Western Ontario and a Bachelor of Theology from St. Peter's Seminary in London, Ontario. That same year he was ordained to the priesthood on May 5, 1973 in the Cathedral of Christ the King, Hamilton, by Most Reverend Paul Reding.
While studying in Rome, specializing in sacred scripture and the Book of Revelation, he received his Licentiate in Sacred Scripture from the Pontifical Biblical Institute in 1978 and a Doctorate in Theology from the Gregorian University in 1986.
After holding various academic appointments, in 1997 he was appointed as Bishop of Saint Paul, Alberta. Two years later, he was named the Archbishop of Edmonton. In 2001, while in Edmonton he was named Apostolic Administrator of Saint Paul. In December 2006, he was appointed as the Archbishop of Toronto, and installed in January 2007.
In 2007 Cardinal Collins became a ex-officio member of the Canadian Conference of Catholic Bishops Permanent Council, the Chancellor of the University of St. Michael's College and the Pontifical Institute of Mediaeval Studies, in Toronto. He is the Chair of the Board of Governors of St. Augustine's Seminary, and the Chair of the Board of Directors of Redemptoris Mater Missionary Seminary, Catholic Charities and Catholic Cemeteries and is a Trustee of ShareLife's Advisory Board. In 2008, Cardinal Collins was elected President of the Assembly of Catholic Bishops of Ontario.
During his time thus far in Toronto, Cardinal Collins has served the global church through his membership with the Pontifical Council for Social Communications, Congregation for Catholic Education and Commission of Cardinals for oversight of the Institute for the Works of Religion (IOR). He has participated in the Synod on the Eucharist, and the Synod on the Middle East, served as an Apostolic Visitor in Ireland and also as the Delegate of the Congregation of the Doctrine of the Faith for Anglicanorum Coetibus.
On January 6, 2012, the Holy Father, Pope Benedict XVI announced the appointment of Cardinal Collins to the College of Cardinals. He was elevated to the College of Cardinals as Cardinal Priest of San Patrizio on February 18, 2012.