 He received his episcopal consecration on the following 29 October from Cardinal Pietro Fumasoni Biondi, with Archbishops Carlo Salotti and Domenico Spolverini serving as co-consecrators, at the chapel of "Collegio de Propaganda Fide" in Rome.Marella was named Apostolic Delegate to Japan the next day, on 30 October.In 1942, when the Vatican accepted "de facto" diplomatic relations with Japan, Marella was given "full diplomatic privileges".