The Diocese of Alleppey is along the Arabian sea between the Diocese of Cochin and Quilon. It has an area of 33 sq. kms. The total population in the diocesan territory is about 7,00,000. The Catholic population is 1,35,000. The Diocese was erected on the June 19, 1952 bifurcating it from the Diocese of Cochin. In 1570 the Jesuit Missionaries started to work among St. Thomas Christians in this area. Because of their missionary zeal, 5 churches were built: Holy Cross church Purakkad 1570, St. Andrew's church Arthunkal 1581, St. Michael's church Kattor 1590, Holy Cross church Kadakkarappally 1620, St. George church Manakodam 1640 (rebuilt).
After the schism of the Coonan Cross, the St. Thomas Christians of the mission of Arthunkal were reconciled to Rome by Msgr. Guseppe Sebastian's during his second tour of Malabar in 1662. Even after the capture of Cochin by the Dutch, the Jesuits continued to look after the Christians of this area till about the middle of 18th century. Then the mission was taken over by the Carmelite Missionaries and remained under the Vicariate of Verapoly till the restoration of the Old Cochin diocese in 1886. Bishop Michael Arattukulam was the first bishop of Alleppey (1952 -1984). He passed away on March 20, 1995.