Pope John XXIII wanted the Catholic Church to engage in the contemporary ecumenical movement. He established a Secretariat for Promoting Christian Unity on 5 June 1960 as one of the preparatory commissions for the council, and appointed Cardinal Augustin Bea as its first president. The secretariat invited other churches and world communions to send observers to the council.
The Secretariat for Promoting Christian Unity prepared and presented a number of documents to the council:
The PCPCU has two sections dealing with:
The council has a twofold role:
Since its creation, it has also established a cordial cooperation with the World Council of Churches (WCC). Twelve Catholic theologians have been members of the WCC's Faith and Order Commission since 1968.
The PCPCU is responsible for naming Catholic observers at various ecumenical gatherings and in its turn invites observers or "fraternal delegates" of other churches or ecclesial communities to major events of the Catholic Church.
At present, the PCPCU is engaged in an international theological dialogue with each of the following churches and world communions:
Directed by a Cardinal President, assisted by a Secretary, a Joint Secretary, and an Under-Secretary.
The council is responsible for working with other churches on ecumenical translations of scripture, and promoted the establishment of the Catholic Biblical Federation.
The Commission of the Holy See for Religious Relations with the Jews is the responsibility of the PCPCU, while the Commission of the Holy See for Religious Relations with Muslims comes under the direction of the Pontifical Council for Interreligious Dialogue. This is because when the council was being created the Commission of the Holy See for Religious Relations with the Jews was consulted as to whether it wished to come under the Inter-Religious Dialogue Council, it declined and thus remains part of the Promoting Christian Unity Council.