Headed ex officio by the Malankara Metropolitan and based at the Catholicate Aramana, Devalokam, the diocese is the seat of the Church's supreme leadership.
Before gaining independent status, most historic parishes of this territory were governed directly by the Malankara Metropolitan, a custom predating the Synod of Veliyanad of 1877. When the synod, convened under Patriarch Ignatius Peter IV, organised the Church into seven regional dioceses under Pulikkottil Joseph Mar Dionysius II, these core churches remained under the Malankara Metropolitan, an arrangement confirmed in 1958 by Baselios Geevarghese II at the unification of the Church's factions.
The modern diocese was established on 21 April 1982 by Kalpana No. 110/82 of Baselios Marthoma Mathews I, who divided the Diocese of Kottayam into Kottayam, Kottayam Central and Idukki. By design the Malankara Metropolitan is ex officio Diocesan Metropolitan, a role held successively by Baselios Marthoma Mathews II, Didymus I, Paulose II and the present head, Baselios Marthoma Mathews III. The diocese is therefore headquartered at the Catholicate Aramana, Devalokam, Kottayam, the supreme seat of the Church, and includes prominent historic parishes such as Kottayam St. Mary's Cheriapally and the Mar Elia Orthodox Cathedral.
2 districts, listed alphabetically.