Most historic writings testify that the island was first inhabited by the Pelasgous, then the Phoenicians, Cares and Leleges. These tribes were finally removed from Sifnos, as the Cretan King Minoan had ordered. The oldest traces of inhabitance in the history of Sifnos were found in the Neolithic times. Excavations have revealed small settlements in Kastro, as well as vestiges of an imposing acropolis at the site of Agios Andreas. In the Late Bronze Age (1600 BC), Sifnos came under the cultural and commercial domination of the Minoans of Crete. In 1400 BC, the explosion of Santorini destroyed the main centers of the Minoan civilization. The Mycenaeans took control of Sifnos and the other islands of the area. Today, Sifnos has an important number of Mycenaen findings.
Between 1130 and 1120 BC, the Ionians colonized Sifnos as well as the rest of the Cycladic complex. During that time, the new capital of Sifnos was established in Kastro. The high artistic, commercial and cultural development of Sifnos during this period is proved by the numerous marble buildings, bases of the column, various objects, graves, water supplies, and various sanctuaries. In the 6th century BC, the inhabitants of Sifnos were very wealthy due to the gold and silver mines of the island. This wealth is shown from the Treasury of the Siphnians in Delphi, where valuable items were stored.
A few years later, due to the lack of deposits, the local economy declined. During the Roman and Byzantine years, Sifnos was an exiled land. In 1207, Sifnos fell under the authority of Marko Sanudo, Duke of Naxos, who had by then all of the Cycladic Islands under his influence. Then Sifnos was ruled by a Spaniard and later it was given as a dowry to Nicolas Gozzadino of Bologna. Sifnos remained under the influence of the Gozzadini dynasty until 1537.
The culture of Sifnos flourished that time and in fact, a Greek school was established, the school of Agios Tafos. During the Greek Revolution of 1821, Sifnos joined the fight against the Turkish rule, led by Nikolas Chrysogelas.