The city of classical times was founded around the 9th century BC, probably the port of Lefkada, 15 km west. The city's name comes from the greek words “eretes” = paddler, although Strabon notes that the former name of Eretria was Arotria. Lefkadi was  burned in 825 BC, and that gave the opportunity to Eretria to be developed as  a local power.

The first mention of Eretria was made by Homer in Iliada, appearing on the list of ships marched against Troy (Trojan War). In the 8th BC century, Eretria and Chalkis nearby, were the most prosperous cities of Evia. Eretria controlled Andros, Tinos, Kea in the Cyclades. Also owned and part of the opposite coast of Boeotia. Eretrians together with Chalkideans , founded colonies in southern Italy: Pithikouses  and Kimi.

But in the late 8th century BC , there was a conflict between Eretria and Chalkis, battle that lasted several decades. Thucydides gives us details of this conflict that became known as Lilantios War, the name of a small valley near Eretria. Eretrians were defeated and lost many of their possessions.

Eretria continued colonization of areas in the northern Aegean Sea, in Italy and Sicily.
In 499 BC during the Ionian Revolution, Eretria along with Athens, supported the cities of Ionia against the Persians. After the failure of the revolution, the Persian king Darius I, wanting to avenge this action, besieged and destroyed the city during the Persian expedition of Datis and Artaphernes in 490 BC. At the destruction of the city the temples were not respected, and even the magnificent temple of Apollo was destroyed.

Eretria was built again, and took part in the Battle of Plataea with 600 soldiers (479 BC). In the 5th century BC was part of the First Athenian Alliance. In 446 BC , Eretria was removed  from the alliance, but eventually returned.

During the Peloponnesian War , Eretrians were allies of the Athenians against the Spartans. In 411 BC took part in the so-called battle of Eretria in the area between Athens and Sparta after the battle all the cities of Euboea revolted against the Athenian oppression. After the victory of Sparta in 404 BC, Athens gradually rejoined again and established leadership position in the area of Evia, which was rich in grain. Eretrians rebelled again in 349 BC. In 343 BC Philip II of Macedonia had the city under his control, but in 341 BC, the Athenian general Demosthenes  subjugated the town.

After the Battle of Chaironias (338 BC), in which Philip defeated the coalition army of Athens and Thebes, marked the definitive end of Eretria as an important city-state. The city continued to exist as a small provincial town. In 198 BC , it sacked by the Romans in 87 BC and was destroyed during the Wars Mithridatic and was eventually abandoned.