Pope Pius XI appointed Serafini as Governor of Vatican City in 1929, on the foundation of the State, and he remained in office until his death in 1952.
[7] In 1943, he signed with the German-controlled Italian Social Republic the guarantee of extraterritoriality for religious buildings not included in the Lateran Treaty.
[8] On 20 December 1939, the king and queen of Italy made a further state visit to the Vatican, and Serafini read an address to welcome them.
[9] In 1950, Charles H. Doyle described Serafini as "a colorful layman" who was a frequent visitor to Pope Pius XII.
[11] The marquis was a cousin of Cardinal Domenico Serafini, who served as Prefect of the Sacred Congregation for the Propagation of the Faith between 1916 and 1918.