Initially built by the Bhadurshah of Gujarat and further developed into a state of the art fort by the Portuguese, conquered by the Marathas and finally neglected by the British the last rulers of Vasai pre independence. The Vasai fort has stood witness to many times and periods in history.

Unlike other forts which are built to strengthen strategic points having warfare material and housing soldiers, the Vasai fort was actually a fort city complete with churches, hospitals, college institutions, and other administrative and community places. It was not surprising then that the Portuguese used it as their commercial and military base on the North western coast in India. Surrounded on three sides by the sea and only accessible by land on one side the Vasai fort proved tough to conquer. A very high (30 to 35 ft.) and strong wall (30 to 40 ft) on the land side made it the impenetrable fort ever. The Portuguese were known fierce sea farers and they had a large fleet defending the fort from the sea side making this fort completely invincible.
The fort was also used as an official residence of the Portuguese Governor when he made his visits to the North. Hence there was a regular large soldier base stationed here.

The Portuguese took over the mud and clay fort like structure from the ruling muslim bastion on the day of St. Sebastian in 1534 and hence they also referred this fort as Fort St. Sebastian. It took them more then 30 years to remodel the original structure into a very strong fort. The fort relics, today clearly signify the planned structures. The fort arrangements and layout were similar to the ones in Portugal and hence it became a popular colony for the Portuguese and is also described in there literatures. The very wealthy of Portuguese visited the fort and found pride in making it there home in India.
 
In 1739 The Maratha warrior Chimajiappa laid seize to the fort. After a bloody battle of months and daredevil feats, he was finally able to enter the fort. The valiant Marathas incurred great human losses to acquire this fort whereas the Portuguese did not lose much except for the fort and the territory surrounding it. It was but an end of the 205 year old Portuguese regime in this region.
In the treaty that followed, Chimajiappa generously allowed the Portuguese to leave the fort with whatever they wished to carry along and they were allowed ample time for it. The Portuguese carried along with them many valuable artifacts of the fort along with there personal belongings. The Marathas then entered the fort and built two temples in the fort to thank the mother goddess Vajreshwari and Shiv Mahadeo in achieveing this feat, this were the only structures added by the Marathas in the fort.

The Marathas had their capital in Pune, so the affairs of the fort were entrusted to a Subhedar and Chimajiappa returned back. The Marathas when they attacked Vasai, had no real interest in the fort except to check the missionary activities in Vasai. Gaining the fort that too, after losing many trusted men, the fort was never considered as a reward by the Marathas. The soldiers left behind by Chimajiappa were not wishfully willing to stay back. After the great human loss they considered the fort a haunted place and also feared losing religious values staying in a place of Christian domain. Hence the fort remained mainly neglected in the Maratha regime. Further in 1818 the fort was passed on to the British as part of a treaty.

The British, by then had developed the neighboring port city of Mumbai which was under there rule and hence ignored the Vasai fort at large. They only exploited it for commercial use like a leased sugar mill in one of the church premises. Many structures in the fort were demolished to make way for commercial utilization of the place. Natives of the region also carried stones from these dilapidated and unguarded structures to build there homes.

Today the fort site is governed by the ASI and awaiting the much delayed restoration process.