The Eparchy of Thamarassery is an Syro-Malabar Catholic Church eparchy in India, under the Syro-Malabar Catholic Church. It was created on 28 April 1986. On Monday, 18 January 2010, the Synod of Bishops of the Syro-Malabar Church, meeting at Mt. St. Thomas (with the assent of the Holy See) appointed Remigiose Inchananiyil, secretary and chancellor of Thamarassery, and judge of the major archiepiscopal tribunal, as the new bishop. Remigius Inchananiyil was consecrated on 8 April 2010.

The Syro-Malabar Church is governed by the Major Archbishop of Erankulam-Angamaly and the synod of all bishops of the sui iuris Church, both within and outside of India.

Eparchy of Thamarassery comes under the Province of Tellicherry. There are several important churches under the Eparchy of Thamarassery. The most prominent among them are St. Thomas Forane Church Koorachudu and Sacred Heart Forane Church Thiruvambady.

• Karuvarakundu Holy Family Church (1972)
• Kodenchery St.Mary's Church (1949)
• Koorachundu St. Thomas Church (1947)
• Malappuram St. Thomas Church (2005)
• Marudonkara St.Mary's Church (1939)
• Paroppady St. Antony's Church (1969)
• Perinthalamanna St. Alphonsa's Church (1995)
• Thamarassery Mary Matha Cathedral Church (1984)
• Thiruvambady Sacred Heart Church (1944)
• Thottumukkom St. Thomas Church (1960)
• Vilangad St. Georges Church (1968)

Under this 11 Foranes there are 118 parishes, 14 stations also there. Around 30,000 families & 1.30 lakhs members are there total in Diocese.