We have radiocarbon-dated the main settlement of Skarkos (Skarkos II) on the Cycladic island of Ios, using a set of animal bone samples. The site of Skarkos stands on a hill in a coastal plain, mid-way down the western side of Ios island and about 1 km from the island’s harbour. It is the first time this important settlement with a wealth of finds and an extraordinary building system with two-storey houses is dated in absolute terms complementing the chronology of the Cycladic EBA II period. The radiocarbon determinations show that the major phase of the settlement came to an end between circa 2550 and circa 2500 BC. The dates also confirm the archaeological evidence that the main occupation period is dated archaeologically to the EC II period (Keros-Syros culture). Furthermore, in order to embed the new Skarkos dates within the overall Cycladic chronology and define better the end of the EC II phase, we treated the Skarkos dates together with published dates from other Cycladic sites using Bayesian analysis considering two different models.