[1] He served as personal secretary to cardinals Domenico Tardini and Amleto Giovanni Cicognani, as well as in the Council for the Public Affairs of the Church from 1969 to 1979, where he was in charge of the section for international organisations, peace, disarmament, and human rights.

He traveled to Moscow with Archbishop Agostino Casaroli, secretary of the council, to deliver the instrument of adhesion of the Holy See to the Treaty on the Non-Proliferation of Nuclear Weapons in 1971.

He said:[8][9] In that tragic period, [Pius] was concerned about the Germans leaving Rome in peace and respecting its sacred character.

At the same time, however, he worked to see that as many Jews as possible were sheltered in churches and Catholic institutions.... Pius XII considered what had happened to the Dutch bishops a warning not to do the same.

It was precisely the country where priests and bishops most vocally denounced the anti-Jewish persecutions that had more deportations than any other nation of Western Europe.Following the election of Pope Francis in 2013, he said the Catholic Church needs to "start from the Second Vatican Council, from all that has not yet been implemented and must still be accomplished".

He called the work of the council and the plans of Pope John XXIII "an unfinished task" and said the church needs "a new language to talk to humanity today, and in particular to the new generations, and to give adequate answers to modernity".

[10] He was chair of the Collegio universitario Fondazione Comunità Domenico Tardini [it], which was founded in 1946 to support war orphans.

[11][12] In the 1990s, Silvestrini was mentioned as a successor to Pope John Paul II in the secular press, though Vatican observers, such as Thomas J. Reese, noted that his advanced age made his election unlikely.