Luigi Centoz was born on 2 April 1883 in Saint-Pierre, Aosta Valley, Italy. He was ordained a priest on 9 June 1906. In 1909 he joined the staff of the Holy See's Secretariat of State, where he worked directly for the Cardinal Secretary of State Rafael Merry del Val. On 6 January 1921, he was assigned to the nunciatures to Germany and Bavaria (and from 1925 to Prussia), working for the Nuncio Eugenio Pacelli, later Pope Pius XII. He participated in the conclave of February 1922, as aide to Cardinal Merry del Val.