The diocese consists of the Latin Catholics of Malabar residing in the revenue districts of Kannur and Kasaragod.

Diocese of Kannur comprises the territory of the civil district of Kannur to the north of Mahé River, excluding Palloor, Chalakkara, Pandakkal and Cherukallai which belong to the municipality of Mahe and the territory of the civil district of Kasaragod which falls to the south of Chandragiri River.

It was with the advent of the Portuguese sailor, Vasco de Gama who landed here on 20 May 1498, that the missionaries had access to this area.

The four Franciscan missionaries with Hovavo Nova, their group leader were allowed to build a chapel in Kannur.

In 1505, the Portuguese Viceroy, Francis de Almeida, established the famous fort of St. Angelos and built the church of St. James there.