Born in Cà Mau, Vietnam, Asia, Mẫn studied in Cần Thơ and Saigon, and was ordained a priest on 25 May 1965, serving the diocese of Cần Thơ.[citation needed]
After studying in the United States, Mẫn taught in Vietnam for a number of years. In 1993, he was appointed Coadjutor Bishop of Mỹ Tho and promoted to Archbishop of Hồ Chí Minh City in 1998. He officiated at a mass in La Vang in 1998 for the 200th anniversary of the apparition of the Virgin Mary, the largest Vietnamese Catholic event up to that time.[2]
Mẫn was elevated to cardinal in the consistory of 21 October 2003 by Pope John Paul II, and was one of the cardinal electors who participated in the 2005 papal conclave that selected Pope Benedict XVI.
On 7 March 2013, Mẫn was the last cardinal to arrive to attend the 2013 papal conclave to select the successor to Pope Benedict XVI.[3] The conclave subsequently elected Pope Francis.
On 28 September 2013, Pope Francis appointed Bishop Paul Bùi Văn Đọc, previously (since 1999) serving as Bishop of the Roman Catholic Diocese of Mỹ Tho, Vietnam (one of the Archdiocese of Hồ Chí Minh City's suffragan dioceses), as Coadjutor Archbishop of the Archdiocese.[4]
On 22 March 2014, Pope Francis accepted the resignation of Cardinal Mẫn due to age limit. Coadjutor Archbishop Paul Bùi Văn Đọc succeeded him as Archbishop of Hồ Chí Minh City.[5]
