25/08/1893 Established as Diocese of Trincomalee by Pope Leo XIII.
It was under the administration of the Bishop of Jaffna until the creation of the new Diocese.
The new Diocese included three administrative districts of the Eastern Province: Trincomalee, Batticaloa (Ampara) and Polonnaruwa of the North Central Province.
23/10/1967 Renamed as Diocese of Trincomalee – Batticaloa.
19/12/1975 Lost territory (Polonnaruwa of the North Central Province) to establish Apostolic Prefecture of Anuradhapura.
03/07/2012 Renamed as Diocese of Trincomalee.
Lost territory (Batticaloa and Ampara civil districts) to establish the Diocese of Batticaloa. Its first Bishop being Rt. Rev. Dr. Joseph Ponniah.
The civil district of Trincomalee consists of Tamil, Sinhala ethnic groups and predominantly Hindu, Buddhist and Islam religious groups.
The Catholic population of the Diocese of Trincomalee is around 00% of the total population which includes both the Sinhala and Tamil speaking Catholics.