On November 11, 1996 through the Bull, "Apud Indorum" His Holiness Pope John Paul II erected the new Diocese of Thuckalay and appointed Mar George Alencherry its First Bishop. Thus the long cherished aspiration of the faithful of the Kanyakumari Mission and the Archdiocese of Changanacherry was fulfilled.

Thuckalay the first Syro - Malabar diocese of Tamilnadu is a municipal town in the district of Kanyakumari. Thuckalay is 55 kms. South of Thiruvananthapuram and 35 km. North West of Kanyakumari. N.H 47, the National Highway, passes through Thuckalay. The Diocese of Thuckalay comprises the district of Kanyakumari and Taluk of Shenkottai of Tirunelveli District. The language of liturgy is Tamil.

It is in fitness of things to recall with gratitude the three Archbishops by whose paternal care the Church work has grown to a level that has led to the formation of the Diocese of Thuckalay. His Grace the Late Mar Mathew Kavukatt, the founder of the undertaking nursed it and helped it grow and expand. His Grace Mar Antony Padiyara who was well versed in Tamil won over the hearts of the Tamil - speaking people. The work has grown considerably during the fifteen years of his service. Under the pastoral care of His Grace Mar Joseph Powathil the Church work has grown further. The thirty seven years of the mission work was done by the Archdiocese of Changanacherry and the keen interest taken by His Grace, Mar Joseph Powathil led to the formation of the Thuckalay Diocese.

At the time of erection of the diocese, this diocese was granted jurisdiction over the whole Kanyakumari District and the Taluk of Shenkottai of Tirunelveli District in 1996. Total area came to 1,793.94 sq. Kms. Kanyakumari is the southernmost part of India. This District was formerly a part of Thirukkochi State. In the year 1956 on 1st November, Kanyakumari was separated from Kerala and added to Tamilnadu State. The main language of this place is Tamil, but some do speak Malayalam. The Diocese has its Liturgy in Tamil language. 

The territory of the diocese of Thuckalay is extended by the Supreme Roman Pontiff, Pope Francis, on 9 October 2017 from Kanyakumari to Mathurai including the districts of Kanyakumari, Thirunelveli, Thoothukudi, Ramanathapuram, Viruthunagar, Sivagangai, Theni and Madurai of Tamilnadu and at present the total area comes under this diocese is 32,374.30 sq. Kms..

Now the Diocese of Thuckalay has 57 parishes and 11 Mission Centres (Total 68), which have the strength of about 30,130 people. At present 51 diocesan priests, 5 non incarnated priests from other dioceses, 25 religious priests (CMI - 14, MCBS – 7, MST – 2, and SDB – 2), and 290 religious sisters belonging to 16 Congregations and a Secular Institute are serving the Diocese of Thuckalay.

The Diocese of Thuckalay in its Church extends its concern for the spiritual, educational, social, health, economic and other needs of the people irrespective of caste, creed or religion.