In 1537 A.D., Syros was under Turkish oppression.

The population of the island at that time amounted to about 3. 000.

It suffered from repeated invasions of pirates, who, in turn, were at war with the Turks.

In 1617, the Catholic bishop Andreas Kargas was condemned to the gallows by Captain Ali Pasha. These events resulted in an important decrease of the island's population.

In 1633, Capucine monks settled on the island. In the middle of the18th century, Jesuits and Ursulines took over the education and medical care for the people of the island.

Towards the end of the 18th century, Turkish power declined. Representatives of the Turkish kadis (senior officers) lived on Andros. There were no Turks on the island. The concession of the island's catholic church passed from Turkish into French hands. A bishop was appointed by the Pope. Bodies of local self-administration (Assembly, committee, deputation) were founded. Thus, the basis for further economic development was established.

During the 2nd Russian-Turkish war, the islands were liberated (1770-1774). However, by the Treaty of Kioutchouk- Kainardji, they were again passed to the Turks. Syros appeared to be in favour: Sultan Abdul Hamid made it a gift to his niece Sah, who relieved the island of its tax burden.

The island did not actively take part in the Greek revolution of 1821, being under French protection at that time. Neither was it a considerable maritime power. However, it supported the revolution financially and accepted refugees from Chios, Izmir and Psara, who were persecuted by the Turks and had to escape to a safer place. It were these refugees who built Hermoupolis, which soon became one of the most important centres of the new Greek state. The "miracle" of the city of Hermoupolis was wrought thanks to the efforts and the commercial talents of these people.