Santa Maria in Domnica
Pope Benedict XV created him Cardinal-Deacon of Santa Maria in Domnica in the consistory of 4 December 1916. Marini, who never became a bishop, was named to the Commission of Historical Studies on 4 January 1917. He was made Secretary of the Sacred Congregation for the Oriental Churches on 29 November 1917, essentially serving as head of that congregation as the Pope was the nominal Prefect at that time. Cardinal Marini resigned his post because of his advanced age and poor health in 1922. During that same year, he participated in the papal conclave that selected Pope Pius XI. One of his last appointments was as Protector and Visitor of all the Oriental Institutes of Rome on 28 July 1922.