On 28 January 1932, Chiarlo was made Apostolic Internuncio to Central America, with responsibility as Nuncio to Costa Rica, Honduras, Nicaragua, El Salvador, and Panama, as well as Apostolic Delegate to Guatemala.[3] His role was then modified on 30 September 1933 with the erection of nunciatures, leaving him Apostolic Nuncio to Costa Rica, Nicaragua, and Panama, with his role as Nuncio to El Salvador and Honduras and Delegate to Guatemala assigned to Albert Levame later that year.[3][4]
Returning to Rome, he was charged with the special mission of assisting prisoners of World War II on 3 December 1941. He was named head of the pontifical mission to Germany in 1945.
He was appointed Nuncio to Brazil, where he would be a beloved figure,[5] on 19 March 1946.[6] He was replaced in Brazil by Armando Lombardi on 22 September 1954[7] and remained a nuncio at the disposition of the Secretariat of State.