Ordained a priest of the Archdiocese of Indianapolis in 1970, he served on the CUA faculty from 1973 to 1978 and, after teaching at several other institutions, returned to Catholic University in 1983. He was appointed to a permanent position as dean in September 2000.
One of his key accomplishments as dean was to lead the school through a reorganization to streamline the way it offers degree programs, the university said in a statement. The restructuring, which took effect last August, included the replacement of the school's four departments with seven "academic areas."
Monsignor Happel was named by Cardinal Theodore McCarrick, archbishop of Washington, as his personal theologian in 2002. John Paul II honored him with the title Chaplain to His Holiness and monsignor last spring.