The patron saint of Rezzo is Saint Martin, bishop of Tours, celebrated on 11 November. The parish church dedicated to him, in the historic centre, was built in the 17th century and holds inside the remains of a 16th-century polyptych by an unknown painter and an old slate baptismal font; the oratory of the Saints John the Baptist and Evangelist is attached to it.
Rezzo was, since the Middle Ages, among the feudal holdings of the marquises of Clavesana. In the 14th century the territory was contested among the marquises of Ceva, the Del Carretto and the Clavesana themselves, until Emanuele II of Clavesana ceded part of the territory to Genoa in 1385; a new dispute in the following century ended with the reunification of the holdings under Gaspare Clavesana, who purchased the half still in the hands of the Del Carretto. The family's more stable rule, under the influence of the Republic of Genoa, brought profitable economic and architectural development to the village, with the building of the residential palace and the restoration of the parish church, until 1784, when the vassalage passed to the Genoese nobleman Paolo Girolamo Pallavicino. In the hamlet of Cenova stands the church of Nostra Signora Assunta, built in the 15th century and rebuilt in Baroque style between 1684 and 1702 by Gio Batta Marvaldi.
