In 1916, he entered the seminary to become a Roman Catholic priest. He was ordained priest on 29 May 1920 in Brescia and celebrated his first Holy Mass in Brescia in the Basilica of Santa Maria delle Grazie. Montini concluded his studies in Milan with a doctorate in Canon Law in the same year. Afterwards he studied at the Gregorian University, the University of Rome La Sapienza and, at the request of Giuseppe Pizzardo at the Accademia dei Nobili Ecclesiastici. At the age of twenty-five, again at the request of Giuseppe Pizzardo, Montini entered the Secretariat of State in 1922, where he worked under Pizzardo together with Francesco Borgongini-Duca, Alfredo Ottaviani, Carlo Grano, Domenico Tardini and Francis Spellman. Consequently, he spent not a day as a parish priest. In 1925 he helped found the publishing house Morcelliana in Brescia, focused on promoting a 'Christian inspired culture'.

In what year did Montini enter the Catholic seminary to become a priest?