Champakulam Church or the Basilica of St. Mary's is thought to be one of seven churches thought to be established by Saint Thomas when he came to Kerala in AD 427 to evangelise, and one of the oldest churches in India. This church which is on the banks of the Pamba river, in Alappuzha, is a Syro-Malabar Church, and the mother church of almost all the Catholic Syrian churches in Alleppey. The church has had connections with the Devanarayanans, the kings of the kingdom of Chempakassery; who had their headquarters in the Ambalapuzha Sree Krishna Swamy Temple. The church was well-connected to Puthenkoottukkar, the Malankara church, and played a large role in ecumenical movements in the 18th century.

Festivals and Traditions
The church celebrates two annual festivals, not including the usual Christian festivals like Christman, Good Friday, Easter, etc. The Feast of Mother Mary, or Marian apparition, lasts for 11 days, ending on the closest Sunday after 15 October.

On the 19th of March, a shradha/chatham is performed for St. Joseph, a rite performed in commemoration of his death. Thousands of devotees travel to Kalloorkadu for these two festivals. 

Champakulam church participates in the well-known boat race called Champakulam Moolam, along with the Ambalapuzha Sree Krishna Swamy Temple. This boat race is done annually to commemorate the Procession of an idol of Krishna to Ambalapuzha, and the church provides rope and bamboo as a custom.

Moonnu Noyambu Perunnaal, the Rogation of Ninevites, was a three day fast that was held regularly, but has been recently stopped. The Kings of Chempakassery provided help with the feast for the festival.

Religious elements
Portuguese influences can be seen in the decorated madbaha, these could be modifications made by missionaries. It is also famed for its ancient murals. The church also has ancient rock inscriptions that depict the church's history.

Champakulam church has a Rock Cross on the grounds. It is ancient, with documentation dating it to AD 1151

Ikkako Kathanar
Ikkako Kathanar was a priest of St. Mary's who was martyred by the Portuguese carmelites for keeping the East Syriac tradition of the Nasranis, the Catholics of the indigenous Malayali tradition of Christianity.