He was ordained a priest on 23 November 1941 in Auckland, and received episcopal consecration in Rome from Pope Paul VI on 30 June 1974.
With the passage of the Private Schools Conditional Integration Act 1975, while he was Bishop of Auckland, Mackey played a key role in the integration of Catholic schools into the state system,[3] developing a close working relationship with the Minister of Education, Merv Wellington.
[6] In the earlier years of his retirement, Mackey was a guest lecturer in New Zealand and abroad and conducted occasional courses in Church History at Holy Cross College.
He supervised the preparation of the new faith education programmes for Catholic secondary schools on behalf of the New Zealand bishops.
Until shortly before his death, Mackey continued to write on a variety of subjects, including reviews and reflections for Catholic publications.