Historically, the town's countryside is a large producer of chestnut, which has received the European Protected Geographical Status.

The current town was however founded in the 5th-6th centuries AD as Massa di S. Ambrogio.

Starting from the 10th century, there were fortifications and castles, whence the toponym Castrum Rivi from which the current name derives.

In 1076 the castle was acquired by Matilde of Canossa; later Emperor Otto IV gave the fief to the Alidosi family, who held it for more than four centuries until it became part of the Papal States.

During World War II Castel del Rio was located across the Gothic Line.