The history of Agistri dates back to the ancient years when the island was known as Kekrifalia, (embellished head). In fact, archaeological excavations suggest that the first traces of human inhabitancy on Agistri are estimated 2,500 years ago. However, the island was not continuously occupied. Its early inhabitation gave it some important apparitions on literature, among which the Iliad of Homer. The poet mentions its contribution in the Trojan War as an ally of Aegina Island. In addition, Thucydides and Diodoros mention the island of Agistri, using its original name.
Agistri was part of the Aegina kingdom, along with other neighboring islands, like Aponissos, Kontari, and Megaritissa, which also count on important archaeological findings. The group of islands that formed the kingdom of Aegina was governed by King Aeakos. That is why the histories of this kingdom and the island of Agistri are usually related.
In the Medieval times, Agistri followed the historical course of all Greece: at first, it was part of the Byzantine Empire and then it was conquered by Ottomans. Like the rest of the Saronic islands, Agistri was part of the first modern Greek Stata, as formed after the Independence War of 1821. The Royal Decree in the year 1835 established a municipality that gave evidence of 248 inhabitants in Agistri. In the early 1970s, another important service was available on the island: electricity. In addition, an asphalt road around the island was constructed. Today, the economy of Agistri is based on tourism and agriculture.