The Syro-Malabar Catholic Archeparchy of Thalassery is an ecclesiastical province of the Syro-Malabar Church in Kerala, India, and covers the territory of Kannur and Kasargode districts in Kerala. The Diocese of Tellicherry was erected on 31.12.1953 by the Papal Bull Ad Christi Ecclesiam Regendam of Pope Pius XII, against the backdrop of large-scale migration of thousands of Syro-Malabar Catholics from South to the Northern forestlands of Kerala. The boundaries of the new diocese were the same as those of the Latin Diocese of Calicut. But later, as Catholics of Syro-Malabar Church migrated even to the states of Karnataka and Tamil Nadu, the boundaries were extended to the present Latin Diocese of Mangalore, Chikmagalur, Mysore, Shimoga, and Ootacamund by a decree of the Holy See dated April 29, 1955. The diocese covers an area of approximately 4,902 km² and a Catholic population of 273,826. Since 2022, Mar. Joseph Pamplany is the Metropolitan Archbishop.

The history of the Malabar Migration and the ecclesiastical province of Thalassery are closely connected. The Thalassery diocese took up the struggle of the settlers, mainly Syriac Rite Catholics. Petitions were sent to the Holy See by the bishops of the settlers, who had migrated to British Malabar since 1930, requesting their own diocese. Cardinal Tisserant, the Prefect of the Oriental Congregation, came to Malabar and personally saw the pitiable situation of the settlers. With the help of locals and priests, they started to make changes in the region.

Bishop Mar Sebastian Valloppilly was appointed as its first Apostolic Administrator. He took charge of the diocese on 19.03.1954. Later he was elected as the first bishop of Tellicherry on 16.10.1955 and ordained on 08.01.1956 at St. Peter’s Basilica by Cardinal Eugene Tisserant.

The diocese was bifurcated in 1973, and the diocese of Mananthavady was erected on 01.03.1973. Again, the Diocese of Tellicherry was bifurcated twice, on 28.04.1986 to form the Diocese of Thamarassery and on 24.04.1999 to form the Diocese of Balthangady. On 01-05-1989, Mar Sebastian Valloppilly retired, and Mar George Valiamattam Was consecrated as his successor. The diocese was raised to the stature of Metropolitan Archdiocese by the Papal Bull Spirituali Bono Christi Fidelium of Pope John Paul II on 18.05.1995. The Archdiocese enjoyed the gracious leadership of Archbishop Mar George Valiamattam from 01.05.1989 to 30.10.2014. On his retirement, Archbishop Mar George Njaralakatt was installed as the new Archbishop of Tellicherry on 30.10.2014. He assumed office on the same day. Mar Joseph Pamplany was elected as the first auxiliary bishop of Tellicherry by the Holy Synod of the Syro-Malabar Church, and his Episcopal consecration was held on 08.11.2017 at St. Joseph’s Cathedral Church, Tellicherry. On the retirement of Mar George Njaralakatt on April 20, 2022, Mar Joseph Pamplany was installed as the Archbishop of Tellicherry.