The village history is lost at the beginning of the 19th century when the settlement was named Zagarena (Greek: Ζαγάρενα). The name changed after the name of a local spring of "Koromilia" in the middle of the 20th century.
The main occupation of the inhabitants, historically, is stock and mixed farming.
Koromilea is well known in the area for the feasting which takes place every 14 and 15 of August in honour of the religious event of the Dormition.
The dominant family names in Koromilea are Tserpes, Krompas, Konstantakopoulos (Greek: Τσερπές, Κρόμπας, Κωνσταντακόπουλος).