[2] Born in San Isidro, Buenos Aires, Copello studied at the seminary in La Plata and the Pontifical Gregorian University in Rome before being ordained to the priesthood on 28 October 1902.

Pope Pius XI created Copello Cardinal-Priest of San Girolamo dei Croati in the consistory of 16 December 1935, making him the first cardinal from Argentina and Spanish America.

Raised to the rank of Primate of the Church in Argentina on 29 January 1936, Copello was one of the cardinal electors in the 1939 papal conclave that selected Pope Pius XII.

In November 1945, he prohibited Argentine Catholics from supporting parties or candidates who promoted the separation of Church and State, removing religion from public schools, or legalizing civil divorce in the February 1946 elections.

He resigned, after twenty-six years of service, as Buenos Aires' archbishop on 25 March 1959, and was appointed Apostolic Chancellor on the same date (remaining in that post until his death).