The diocese of Idukki was erected by His Holiness Pope John Paul II bifurcating the diocese of Kothamangalam. The bull of creation ‘Maturescens Catholica Fides’ was promulgated on 19-12-2002, the declaration was on 15-01-2003 and the Eparchy was inaugurated on 02-03-2003. The eparchy is dedicated to MAR SLIBHA.

Nature and specialty of the area
The name of the district 'Idukki' is supposed to be derived from the Malayalam word 'idukku' which means a narrow gorge. The river Periyar, which is one of the largest rivers of Kerala, is flowing through Idukki and the gorge formed between the two high massive hills called "Kuravan" and "Kurathi", is the site of the gigantic Idukki Arch Dam. The total area of the diocese is covered by the mountainous hills and valleys, and dense forests. Due to its special landscape it is known as the Diocese of the Mountains.

High Ranges vary in altitude from 2000 ft above mean sea level (M S L) to more than 6000 ft. The different levels of elevation promote the diversity of vegetation in this region. The hills touching the skies and being skirted round with thick rain- fed sylvan forests render a specific charm to the region. The climate is comparatively moderate with a temperature varying between 5 to 30 degrees. However, in the hot summer the days are very warm. The nights have a moderate temperature. In peaks above an elevation of 2400 m. the temperature at times goes down to below zero in the cold months of December and January. Occurrence of mist is usual in the high range region.

Geographical structure of the Diocese
The Eparchy of Idukki lies extended covering an area of about 3000 sq. km. The Eparchy is situated in the eastern part of Kerala, surrounded by the eparchies of Kothamangalam, Kanjirappally, Pala and the Archdiocese of Madura. The boundaries of the diocese are:

North: Cheeyapara-Uzhuvathadam river
East: Kerala Tamilnadu boundary
West: Western Boundary of Kanjikkuzhi and Vazhathope Panchayats
South: Kinginithode- Vazhipuzha Rivers and the eastern boundary of Arakulam village, and Idukki Reservoir.

Population & Language
The eparchy has a total population of about 757694 of which:

The Languages spoken are Malayalam 95% and Tamil 5%. The figures in the list can vary slightly. 

Parishes and Mission Stations
The Diocese is organized under 135 parishes and mission stations spread over 10 proto-presbyterates

Migration to the High Ranges
The district is a place of large migration of people from Kerala's main land and labourers from the neighboring state of Tamil Nadu. About five decades ago almost all the present growth centers in the high range region were thick forests. During 1890-1920, on account of plantation of tea and cardamom, some people came to this place to work in the estates. 1933-47 saw migration on a smaller extent due to the Pallivasal Hydro-Electric Project. During 1940-60 the migration was on account of poverty due to the after effects of the Second World War. During 1946 Government allotted forestland for 2000 families while in 1950 Colonies were established especially for Ex-servicemen.

In 1951 under Grow More Food Scheme 1500 acres of land was allotted to 1000 families, which made more and more people migrate to this district. During 1960’s and 70's many migrated on account of the construction of the Idukki Arch Dam. 

Increased migration caused increase in population in the hilly Taluks of the district, especially Udumbanchola and the eastern parts of Thodupuzha Taluk from 1970 onwards. Lack of industries in the district and the inability of neighboring areas to absorb the labour force, and the backwardness in the educational realm also acted as a catalyst for the large-scale encroachment of forest areas. 

The economy of the region
The economy of Idukki in the high ranges is predominantly agrarian: cardamom, tea, pepper, coffee, ginger, and vegetables are the most important agricultural products of the district. Farmers and agricultural labourers constitute about 80% of the population. More than half of them have only less than half a hector of land to cultivate and a large number of them are daily wage workers. In recent times there is a boom in tourist interest in the region due to the natural beauty of the region. 

Culture
Idukki is having a mixed culture due to the large scale migration to the district from different parts of Kerala and from the neighboring State of Tamilnadu. Christians, Hindus, and Muslims are the three dominant religious groups in this region. Majority of the Christians are middle class farmers