It is said that Saint Francis Xavier, during his travels to Japan and China, briefly stayed at what is now called Uppalam.
Also, members of various religious orders, looked after the spiritual needs of the European communities in their trading centres along the coastal areas like Cuddalore, Porto Novo etc., The French Capuchins first settled in Pondicherry in 1674 and the French Jesuits, expelled from Siam (Thailand) also took refuge in Pondicherry in 1688.
While the Capuchins were looking after the Europeans in Pondicherry, the French Jesuits organized the Carnatic Mission for the Indian people.
Although the bishop of these new missionaries had all the power of jurisdiction, he was not given the title 'Vicar Apostolic', but called as the 'Superior of the Mission of the Coromandel Coast'.
Rome successively gave him the jurisdiction over the Madurai, Coimbatore and Mysore areas, affected by the suppression of the Society of Jesus.
Originally, the archdiocese was looking after the ex-French settlements of the Puducherry Union territory namely Karaikal, Chandranagore, Mahe, and Yanam.