Egaleo was founded in 1931 by Demetrios Haniotis and Georgios Aronis, as Athletic Union of Ierapolis (Αθλητική Ένωση Ιεραπόλεως - Athlitiki Enosis Ieropoleos). In 1946, four clubs in the district merged with Ierapoleos to form Athletic Club Egaleo (Αθλητικός Όμιλος Αιγάλεω - Athlitikos Omilos Egaleo), which managed to reach for the first time the first division in 1961.
In August 2009, a merger between Egaleo and Ilisiakos F.C. took place, as the other club participated in the second division, with the purchase being made effective by Egaleo's owner Thomas Mitropoulos; the new club, which took Ilisiakos' place, was renamed Egaleo A.O.
At the end of the 2009-2010 season, due to the merger being declared illegal by the Greek Council of State, Egaleo F.C. was relegated to the Delta Ethniki.