Born 1921 in Poponguine, Senegal, his father was a catechist. After finishing his secondary studies, he entered the regional seminary of Dakar and was ordained a priest on April 18, 1949, did parish work for two years and then went to Rome for further study at the Pontifical Gregorian University. He returned to Senegal in 1953 and, after working as a chaplain to Catholic action groups, became parish priest of the Dakar cathedral in 1960 and Vicar General the following year.
On May 20, 1962, he was consecrated as Archbishop of Dakar, succeeding Archbishop Marcel Lefebvre. He was proclaimed Cardinal by Paul VI in the Consistory of May 24, 1976, receiving the Title of Santa Maria del Popolo.
Until 1987, he was president of the Bishops’ Conference of Senegal-Mauritania, and an elected member of the Council of the World Synod of Bishops. He has been the President of CEPACS (the Pan-African Episcopal Commission for Social Communications). He also took part in Vatican Council II.
Has been a member of the Council of the General Secretariat of the Synod of Bishops; President Delegate of the 4th General Assembly of the Synod of Bishops (1977); Relator of the 7th General Assembly of the Synod of Bishops (1987); and, General Relator of the Special Assembly for Africa of the Synod of Bishops (1994).
Cardinal Thiandoum died in 2004 at the age of 82.