Finishing his Roman studies in 1931, he then did pastoral work in Colombo until 1945, whilst teaching at St. Joseph's College and serving as a university chaplain.
He received his episcopal consecration on March 7, 1946 from Archbishop Leo Kierkels, with Bishops Edmund Peiris, OMI, and Bernardo Regno, OSB, serving as co-consecrators.
Cooray succeeded the late Jean-Marie Masson, OMI, as Archbishop of Colombo on July 26, 1947, becoming the first local-born head of the see.
Cooray, the first Sri Lankan member of the College of Cardinals, resigned as Colombo's archbishop on September 2, 1976, after a period of twenty-nine years.
[3] In the first step towards sainthood, Pope Benedict XVI declared him to be a Servant of God on 22 November 2010 after the Congregation for the Causes of Saints gave its approval to begin the canonization cause.