The patron saint of Pornassio is Saint Dalmatius, celebrated on 5 December. The parish church dedicated to him, in the hamlet of Villa, dates from the 15th century.
The fief of Pornassio was long disputed: an imperial appointment claiming control over it drew reaction both from the Del Carretto marquises, who advanced equal rights, and from the lord of Garessio, Giovanni Scarella. It was the direct intervention of the Doge of Genoa, Antoniotto Adorno, that restored a stable situation, entrusting the fief to the Scarella family under the direct rule of the Genoese state; in 1460 the Garessio nobleman Giorgio Scarella ceded part of the territory. In the 17th century, after the reconquest of Pornassio and its castle, the Genoese authorities reacted violently to alleged assistance given by the Scarella to the House of Savoy: the sacking of the stronghold was followed by the killing of a member of the family, Ottavio Scarella, while on 12 August 1625 the marquises Gio Bartolomeo and Luciano Scarella wrote from Pornassio to the Senate of the Republic to clear themselves of charges of treason. Among the territory's other religious buildings is the church of the Annunziata in the hamlet of Ottano, also from the 15th century.
