The early beginnings of the Christian community go back to many centuries. Fr. Ignatius Gomes, a Jesuit priest, made the first reference to the Christians of Mariamnagar in Agartala when he visited them in 1683 says Historian Dr. David Syiemlieh. So Christianity had been here at least from the 17th century? About 200 years later Fr. P. Barbe CSC, the Pastor of Chittagong, visited Tripura in 1843 and he would have come here to minister to the Catholic community opines Dr. Syiemileh. Holy Cross pioneering missionaries Fr. Louis Augustine Verite and Fr. Beboit Adolphe Mercier had visited Agartala in 1856 and administered Sacraments to the Christians in Mariamnagar Village. But it was only from 1937 that Priests began to take up permanent residence at Mariamnagar. The first Parish in Tripura was erected at Mariamnagar in 1939 and the first permanent Church was blessed in 1952. Because of its geographical proximity, the Archdiocese of Dhaka would continue to cater to the spiritual needs of the Catholics in Tripura till the erection of the new Ecclesiastical Unit in 1952, namely, the Prefecture of Haflong, when Msgr. George Breen, CSC, was appointed the Prefect Apostolic. In 1969, the Prefecture was upgraded to the position of a Diocese and Most Rev. Denzil D’Souza, was elected the first Bishop of Silchar. At that time the Diocese comprised the States of Mizoram and Tripura and the two Districts of Cachar in Assam.
By the Papal Bull VENERABILES FRATRES NOSTRI dated 11th January 1996, Pope John Paul II decreed the erection of the Diocese of Agartala. The new Diocese of Agartala, which comprised the whole State of Tripura, was bifurcated from the erstwhile Diocese of Silchar. Fr. Lumen Monteiro, a Holy Cross priest, was appointed as the first Bishop of the new Diocese of Agartala and was ordained and installed on 26 May 1996. The function was held at Holy Cross School Grounds Agartala, at which the Metropolitan Archbishop of Shillong, Most Rev. Tarcisus Resto Phanrang, SDB, presided over the Ordination Rite, which was attended by many Bishops and a huge congregation of people from India and abroad. The Diocese of Agartala is dedicated to Christ the Light of the World with its motto: LEAD US ONWARD (Duc in Altum). The Patron of the Diocese is St. Francis Xavier.
Today the Diocese of Agartala has 24 Parishes and a Catholic population of 49,000 in total of 4.1 million people. The Diocese of Agartala which comprises the entire State of Tripura with 8 Civil Districts has 30% of its population comprising of the indigenous tribal people who come from 19 major tribes. To mention a few: Debbarma, Reang, Darlong, Halam, Garo, Jamatia, Tripura, Molsom, Chakma, Hrankhawl, Bongcher, Mog, Kuki and Lusai. The majority population is non-tribal.
 cfr. Christianity in Tripura, A Paper by David R. Syiemileh, Department of History, North Eastern Hill University, Shillong. p.1
 Some details of the Holy Cross missions in Tripura are reported in the magazine, The Bengalese. It is mentioned that the Holy Cross Fathers had made attempts to enter Agartala several times and they periodically visited the Christians of Mariamgagar in Agartala. However, permission was not given by the Tripura Maharaja till 1937 to the Congregation to have a missionary based in the capital town. Fr. Raymond Massart arrived at Agartala on 6 January that year “with a certain amount of misgiving and in a what-to-do-now condition of mind”. His letter to a friend explaining the difficulties he endured and the satisfaction he received from his new mission is published in the magazine. “The difficulties are that the expenses are always great. At present there is only a small church here and a six by eight kitchen, which the cook holds forth and makes his abode. I do my sleeping in the sacristy and my eating at this table at the rear of the church. Among the list of things needed from Dacca beside a catechist, is a house to live in and possibly a school. I do not know whether the Bishop can pull a couple of buildings out of his pocket or not. I intend asking him for only a temporary hut for the present as it is difficult to foresee where the bulk of semi-nomadic Garos is going to settle down.” The Bengalese, October 1937, p.7