On 18 November 1974, Pierro received a degree in theology from Pontificia Facoltà Teologica "S. Luigi" (the Pontifical Theological Faculty "San Luigi") in the Posillipo quarter of Naples.

He was then diocesan president of the Apostolic Union of the Clergy, regional vice delegate, and national counselor of the same organization.

[2] On 26 June 1981, Pierro was elected Bishop of Tursi-Lagonegro, receiving his episcopal consecration from Cardinal Sebastiano Baggio on 2 August in the Salerno Cathedral.

In July 2008, Pierro was delivered a notice of investigation for fraud against the state and misuse of property.

Pope Benedict accepted his resignation from pastoral government of the Archdiocese of Salerno-Campagna-Acerno called upon Luigi Moretti, the Vicegerent Archbishop of the Diocese of Rome, to succeed him.