Upon returning to the Pontifical Regional Seminary of Salerno, he became the vice rector and professor of art history for several years.

He also served as a lecturer in philosophy, psychology, art history, religion, English, and Spanish at the liceo classico in the parish.

On 17 March 1988, Mugione was appointed Bishop of Cassano all'Jonio by Pope John Paul II.

He received his episcopal consecration on 28 April of that year in the Aversa Cathedral by Cardinal Bernardin Gantin, the Prefect of the Congregation for Bishops at the time.

[1] On 18 February 2016, upon reaching the canonical age limit, Mugione submitted his resignation from pastoral governance of the Archdiocese of Benevento to the Holy See.