The diocese stretches overs a land area of 1793.94 square kilometers and covers the whole of Kanyakumari district and the taluk of Shenkottai in Tiruneveli district. Nagercoil is the biggest town in the diocese. Marthondam, Kulithurai and Thuckalay are also important towns in the diocesan area.
The total population as of 2017 was 2,010,200. Tamils and Malayalees form the major ethnic groups.
Tamil, Malayalam and English are the languages used in the diocesan territory.
On Nov. 11, 1996, Pope John Paul II erected the diocese of Thuckalay and appointed Mar George Alencherry as its first bishop. Thus the long cherished aspiration of the faithful of the Kanyakumari Mission and the archdiocese of Changanacherry was fulfilled.
Towns are governed by municipalities, whereas villages and small towns are administered by local bodies called panchayats. Members of the local bodies are elected by adult suffrage.
The diocesan area is well connected by roads and railway. The nearest airport is in Thiruvanathapuram, the capital city of neighbouring Kerala state.
Government and private operators provide extensive telecommunication facilities in the diocesan area. The diocese is well connected by local cable TV networks.
The literacy rate here is 81.25 percent.