The Diocese of Itanagar is in the state of Arunachal Pradesh in the North East. Erected on Dec. 07, 2005, it comprises of the civil districts: Tawang, West Kameng, East Kameng, Papum Pare, Upper Subansiri, Lower Subansiri, Kurung Kumey, Kradadi, West Siang, East Siang, and Upper Siang. 

The new diocese of Itanagar, bifurcated from Tezpur has an area of 52,283 km2, with 81,786 Catholics, 36 parishes, 20 diocesan priests, 90 religious priests, 8 religious brothers and 157 religious sisters. The parish of St. Joseph in Itanagar is the Cathedral of the new diocese and St. Joseph is the Patron of the diocese.

The first Bishop of Itanagar, Bishop John Thomas Kattrukudiyil, was born in 1948, ordained priest in 1975 and was appointed Bishop of Diphu in 1994. Bishop John has a Licentiate in Sacred Scripture and a Doctorate in Biblical Theology. He was for many years a formator in Seminaries and was also Rector of the regional Major Seminary in Shillong.

No history of the church in Arunachal can be complete without placing the faith, commitment and spirit of perseverance of the early catholic leaders and catechists who resisting all prohibitions and persecutions held on to their faith and proclaimed it in in the villages of Arunachal Pradesh. The seed of faith germinated and took roots under the watchful care of these great missionaries.

The church in Arunachal owes much to a Benedictine brother Prem Bhai, known as the “apostle of Arunachal Pradesh”. His missionary spirit took him beyond all borders into every village in West Arunachal Pradesh. His ability to befriend strangers made him a welcome guest everywhere. It would not be an exaggeration to say that his footprints are there in every village in Itanagar diocese.