The diocese of Idukki is blessed with a vibrant Christian presence. The history of the catholic presence in idukki region is connected with the history of migration and the intense work of the priests and religious from the diocese of Kothamangalam. When the diocese of Kothamangalam was established in 1956 there were only 17 parishes and mission stations in high ranges with occasional presence of priests and Holy Mass. Fr. Zacharias Pittapillil and Fr. Xavier Pulparambil laboured a lot to establish parishes and mission stations in the high ranges. The centre of activity of Fr. Zacharias was Koompanpara and that of Fr. Pulparambil was Nedumkandom. Their contributions were highly remarkable as it was a period where the bare necessities of life in the literal sense were lacking in the high ranges. Lack of travel facilities, inadequacy of medicine, proper food and accommodation facilities in the chilling climate of the high ranges were not obstacles to their zealous work.

Priests who followed their footsteps started schools, dispensaries, and other centers of development. They were the architects of this region. The whole diocese was with the people at the time of the Ayyappancovil-Udumpanchola and Churuli-Keerithodu Eviction. The diocese was in the forefront with relief works in the floods and large-scale landslides which threatened people many a times during the heavy monsoons in the seventies.

In 1963 the high range mission region was divided into four foranes, namely Erattayar, Rajakadu, Vellathooval and Koompanpara. In 1970 Thankamany, Vazhathopu and Parathodu were raised to the status of forane churches and later, Churuli.  The diocese started a vibrant mission of establishing schools to bring the light of education to the children.

The leadership and hardwork of Fr. John Vallamattom as educational secretary of the diocese of Kothamangalam is especially memorable in the development of the high range region.

It was due to the hard work of priests and religious and the faithful in this region that the present structure and style of the region is achieved. In constructing roads and bridges, bringing electricity and other services to the villages, organizing the local public in all fields, the parish priests gave a remarkable leadership. Under the leadership of Bishop Mathew Pothanamuzhi and Bishop George Punnakottil the region has made great progress in all aspects, especially in the field of education .

When the new Diocese of Idukki was erected in 2003 there were 114 parishes and mission stations.

The total number of the Catholic families in the Diocese of Idukki is around 36147. The Catholic families, all the way uphold the traditional catholic customs and practices. Majority of the faithful are deeply religious, God fearing and law abiding. The percentage of Church attendance is above 95% on Sundays. Besides the Catholics of the Syro-Malabar rite there are Latin Catholics and Syro-Malankara Catholics in this region, belonging to the Diocese of Vijayapuram and Thiruvalla respectively. There are Christians of Jacobite and Orthodox Churches besides various protestant denominations.