It was believed until recently that there was no concrete evidence that Christianity prevailed in Goa before the Portuguese arrived, but it was believed that St. Bartholomew, one of the twelve Apostles of Jesus Christ, brought the Gospel and spread it in Konkan, including Goa, just as St. Thomas had done in Kerala and Tamil Nadu, in Southern India.
However, the work of the historian Jose Cosme Costa, Apostolic Christianity in Goa and in the West Coast (Pilar, Goa: Xavierian Publication Society, 2009), makes a case for the existence of Christianity in Goa before the arrival of the Portuguese. He speaks of Goa as a trading centre with the Middle East and with Rome). He suggests that the Apostle Thomas might have made his way over land from northern India to Kerala. He also examines the evidence of the Apostle Bartholomew having done more or less the same thing. Ch. 6 is dedicated to the examination of Pre-Portuguese references to Christianity in Goa. Ch. 7 examines the vestiges of Pre-Portuguese Christian Customs in Goa and the Konkan. Ch. 8 concludes the book with the "latest archaeological discovery": a "Thomas Cross" hidden in a smallish monument, surmounted by a Latin Cross, near the old Goa harbour. The Thomas Cross bears an inscription in Pahlavi, which, Costa reports, was the liturgical language of the church associated with the Metropolitan of Fars. Costa also suggests that the 'Betal' worshipped quite commonly in Goa is a corruption of 'Bartholomew'. Fr H.O. Mascarenhas, reports Costa, even proposed that there were Christian temples dedicated to the persons of the Trinity: Abanath / Bhutnath (Father Lord), Ravalnath (from Rabboni – Rabulna – Rabulnath) / Bhai rav (Brother Lord), and Atman / Bhavka Devta, Santeri, Ajadevi (Spirit). What then happened to this early Christianity, if it did exist? Costa proposes that the Portuguese destroyed the vestiges and forcibly assimilated these Christians to their own form of Christianity. Those who resisted were among those who fled Goa, he says. It could also be when the zealous Bahmani Muslim empire ruled over Goa.
The Portuguese came to India with the ambition of creating an empire and propagating Christianity. The Portuguese missionaries who accompanied the conquerors were the Franciscans, Jesuits, Dominicans, and Augustinians. The Portuguese first reached the west coast of India when Vasco da Gama landed at Calicut in 1498. On 25 November 1510 Afonso de Albuquerque conquered Goa from the Sultan of Bijapur and made it their headquarters since 1530. By 1544 the Portuguese conquered the districts of Bardez, Tiswadi, and Salcette. Around the same time Pope Nicholas V enacted the Papal bull Romanus Pontifex. This bull granted the patronage ("Padroado") of the propagation of the Christian faith in Asia to the Portuguese and rewarded them a trade monopoly in newly discovered areas. Trade was initiated shortly after Vasco da Gama arrived in India in 1498, but the Portuguese were initially not interested in converting the locals. After four decades, the Catholic Church threatened to open Asia to all Catholics.
In 1534 the Diocese of Goa was created from the Diocese of Funchal to serve as a common diocese for the western coast of India, including Goa and the area in and around Bombay. Missionaries of the newly founded Society of Jesus were sent to Goa; the Portuguese colonial government supported the Catholic mission with incentives for baptised Christians. They offered rice donations for the poor, good positions in the Portuguese colonies for the middle class, and military support for local rulers. Many Indians were converted opportunistic Rice Christians who continued to practise their old religion. The Portuguese, in their efforts to keep Christian purity, insisted the converts should avoid anything Hindu. Portuguese rulers insisted the natives should adopt foreign food habits and dress. They also gave European names to the natives. But Konkani Christians wanted to preserve their language, culture and manners. At the same time the Portuguese colonizers in Goa imposed excessive taxes on the native Christians. The taxes were so huge that in 1642 some native Goans sent a memorandum to Lisbon, the capital of Portugal.
In 1542 St. Francis Xavier of the Society of Jesus arrived in Goa and noticed the newly converted Christians were practising their old (often pagan) customs and traditions.
The Portuguese built various churches; the most notable are Basilica of Bom Jesus (Basílica of Child Jesus) built during the sixteenth century—a UNESCO World Heritage Site dedicated to the Infant Jesus—and the Se Cathedral, the largest church in Asia dedicated to St. Catherine of Alexandria, the construction of which was started in 1562 during the reign of King Dom Sebastião and completed in 1619. It was consecrated in 1640. The Our Lady of the Immaculate Conception Church (Nossa Senhora da Imaculada Conceição Igreja) was built in 1540. The Church and Convent of St. Francis of Assisi (Igreja e Convento de São Francisco de Assis), Church of Lady of Rosary (Igreja da Senhora do Rosário), Church of St. Augustine (Igreja de Santo Agostinho), and St. Michael's Church, Anjuna (Igreja São Miguel em Anjuna), built in 1613, were also erected during the Portuguese reign.
Lots more on Wiki .....