 In the 1920s he was sent to Rome by the Argentine episcopacy, together with three other priests, in order to study the organization of the "Azione Cattolica" (the Italian Catholic Action).The Argentine Catholic Action was founded in 1931 following this model.Caggiano was appointed the first bishop of the newly erected Diocese of Rosario on 13 September 1934, for which he was consecrated on 14 March 1935.