He was ordained to the priesthood on August 15, 1908, and further studied at the Pontifical Gregorian University and the Angelicum in Rome, obtaining his doctorates in philosophy and theology.

De Jong succeeded Johannes Henricus Gerardus Jansen as Archbishop of Utrecht and thus Primate of the Netherlands.

[4] De Jong was created Cardinal Priest of S. Clemente by Pope Pius XII in the consistory of February 18, 1946, but could not travel to Rome for the ceremony as he was recovering from a car accident.

[5] However, on October 12 of that year, the Dutch prelate went to Castel Gandolfo to receive his red hat from Pope Pius.

In 1951, de Jong, who was the first resident Dutch cardinal since the Protestant Reformation, had to leave the administration of the archdiocese to his coadjutor, Bernardus Johannes Alfrink.