Father Tedeschini was raised to the rank of privy chamberlain of his holiness on 6 November 1903, and chancellor of the Secretariat of Briefs in the Roman Curia on 20 October 1908.

He received his episcopal consecration on the following 5 May from Pope Benedict, with Archbishop Giovanni Nasalli Rocca di Corneliano and Bishop Agostino Zampini, OSA, serving as co-consecrators, in the Sistine Chapel.

With Spain on the brink of civil war, Pope Pius XI secretly (in pectore) elevated him to the College of Cardinals on 13 March 1933.

In 1950, Pius XII gratefully acknowledged the participation of Tedeschini in preparing the proclamation of the dogma of the Assumption of the Virgin Mary and highlighted his role in the apostolic constitution Munificentissimus Deus.

[2] Sharing a special affection for the Virgin Mary, Pope Pius XII asked Tedeschini to be his representative at the centennial celebrations in Lourdes.