On 11 October 1991, he was appointed Coadjutor Bishop of the Roman Catholic Diocese of Đà Lạt.

On 22 April 2010, he was appointed Coadjutor Bishop of Roman Catholic Archdiocese of Hanoi.

[2] On 4 January 2015, Pope Francis announced that Nhơn would be created Cardinal-priest on 14 February.

[4] In April 2015 he was appointed a member of the Congregation for the Evangelization of Peoples and of the Pontifical Council for Justice and Peace.

Pope Francis accepted his resignation as Archbishop of Hanoi on 17 November 2018.