Fort Tiracol was originally built by Maharaja Khem Sawant Bhonsle, the Raja of Sawantwadi, in the 17th century. The site chosen was a hillock on the northern (right) bank of the Tiracol River, which gave a commanding view of the Arabian sea. The fort was extensively rebuilt by the Portuguese in 1764.

In the 15th century, the Portuguese explored the sea route to India and Pope Nicholas V enacted the Papal bull Romanus Pontifex. This bull granted the patronage of the propagation of the Christian faith in Asia to the Portuguese and rewarded them with a trade monopoly for newly discovered areas.

After Vasco da Gama arrived at Calicut on the coast of Kerala in India in 1498, the trade became prosperous. In 1510, the Portuguese wrested Goa from the Sultan of Bijapur and finally established themselves in Goa. By 1544, they conquered the districts of Bardez and Salcette in Goa.

In 1534, the Archdiocese of Goa was established. Soon missionaries of the newly founded Society of Jesus were sent to Goa, which lead to conversion of many locals to Christianity. In 1542, Francis Xavier, co-founder of the Society of Jesus, arrived in Goa.