In April 2007 Costelloe was appointed an auxiliary bishop of Melbourne and Titular Bishop of Clonard, and was ordained as a bishop on 15 June 2007.
Costelloe was appointed an auxiliary bishop of Melbourne. This was in April 2007. Costelloe was appointed Titular Bishop of Clonard. This was in April 2007. Costelloe was ordained as a bishop on 15 June 2007. This was in April 2007.