 Castaldo received his episcopal consecration on the following 30 June from Cardinal Alessio Ascalesi, CPPS, with Bishops Salvatore del Bene and Salvatore Meo serving as co-consecrators.Pope Pius XII named him Coadjutor Archbishop of Naples, Titular Archbishop of "Thessalonica", and Apostolic Administrator of Pozzuoli on 14 January 1950.Castaldo became Archbishop of Naples on 7 February 1958 and was created Cardinal Priest of "S. Callisto" by Pope John XXIII in the consistory of 15 December that same year.