Kea was once called the Water Island, Ydroussa, and it is believed that the name is connected to the water nymphs, that lived here according to mythology. Because it was such a pretty island, gods got jealous, and sent a lion to ravage the land. The nymphs fled, and as a subsequence, the island dried out. The Keans then asked Apollo's son Aristaeus for help, and he built a temple to Zeus, who apart from being the highest god, also was the one who sent rain. This pleased him, and the nymphs and waters returned, giving Kea a fertile soil with good crops.

The island has been inhabited since Neolithic times. The poet Simonides was born here. In the 13th century, the island was ruled by the Venetians, and 300 years later by the Turks. Meanwhile, Kea was often raided by pirates, and the locals suffered greatly. It is therefore not surprising that Kea was one of the first Greek islands to enroll in the War of Independence in 1821. In 1930, it was liberated.