 Cullen was raised to the rank of Honorary Prelate of His Holiness in April 1982, and served as director of Catholic Social Services from 1983 to 1988.In August 1988, he was named vicar general of the Archdiocese of Philadelphia.On February 8, 1994, Cullen was appointed Auxiliary Bishop of Philadelphia and Titular Bishop of "Paria in Proconsolare" by Pope John Paul II.