His Holiness Pope Paul VI, by the Bull "Quanta Gloria" of March 1, 1973 bifurcated the vast Diocese of Tellicherry and erected the Diocese of Mananthavady. The Diocese comprised of the civil district of Wayanad in Kerala, the Nilgiris district in Tamilnadu and the districts of Shimoga, Chickmangalore, Hasan, Mandia and Mysore in Karnataka.Mar Jacob Thoomkuzhy was consecrated as the first Bishop on May 1, 1973.

On December 31, 1975, by a decree of the Congregation for the Oriental Churches, dated 4th December 1975, ten parishes from the Diocese of Tellichery in the civil districts of Kannur and Kozhikode (at present Malappuram) in Kerala were added to this Diocese. On June 7, 1995 Mar Jacob Thoomkuzhy was appointed as the Bishop of Thamarassery, and the then Proto Syncellus Msgr. Joseph Kaniamattam was appointed as the administrator of the Diocese on July 27, 1995. On January 26, 1997 Bishop Emmanuel Pothanamuzhy CMI was consecrated as the second Bishop of the Diocese. Following his death on 6th April 2003 Msgr. George Najaralakatt who was until then his syncellus was appointed by the Major Archbishop as the diocesan administrator. On 18th March 2004, Fr. Jose Porunnedom, the then Chancellor of the Major Archiepiscopal Curia was nominated bishop of Mananthavady. His Episcopal Ordination and installation took place on 15th May 2004.