The Diocese of Silchar was made up of the district of Cachar, Hailkandi and Karimkanj of Assam State, the entire states of Tripura and Mizoram.

The Diocese was bounded on the west by Bangladesh while the Northern extremity wedges into the segment of a circle which touches from the east khasi Hills of Meghalaya to the Northern Cachar State, on the Southern section the Chn Hills of Myanmar; on the South, the northern extremity of Arakan district of Myanmar.

This eccelsiastical unit was established as the Perfecture Apostolic of Haflong by an Apostolic Brief 'Fit Numquam', dated January 17, 1952, and entrusted to the Holy Cross Fathers of the Canadian Province.

By an Apostolic Constitution of Pope Paul VI 'Omniumm Solicitudo' dated June 26, 1969, the Prefecture of Haflong was raised to the status of as Diocese with the Episcopal See at Silchar.

In December 1983, the northern Cachar Hills district was detached from the Diocese of Silchar and joined to the new Diocese of Diphu.

On 7th February 1996, the entire state of Tripura was cut off from the Diocese of Silchar thereby forming the new diocese of Agartala, in which Rev Fr Lumen Monteiro csc was appointed as its first bishop. His Episcopal Ordination and Installation took place at Agartala on May 26, 1996.

The remaining portion of Silchar Diocese comprises at present the districts of Cachar, Hailakandi and Kaimkanj of Assam and the entire state of Mizoram. By the division of Silchar Diocese on Feb. 7, 1996 the see of Silchar was transferred to Aizawl.

On May 26, 2000, Apostolic See, by Decree No. 2520/00, suspended Bishop Denzil's canonical faculties because of ill health, and appointed Bishop Lumen Monteiro csc, the Bishop of Agartala as Apostolic Administrator sede plena et ad nutum Sancte Sedis.

On November 7, 2001, the Holy See appointed Very Rev Fr Stephen Rotluanga csc, as Bishop of Aizawl; and his Episcopal Ordination took place on February 2, 2002. His is the first Mizo to be raised to the dignity of Episcopal.