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.
Castaldo assumed the position of Archbishop of Naples on 7 February 1958, and was elevated to cardinal priest of S. Callisto by Pope John XXIII in a consistory held on 15 December of the same year.