The patron of Castelnuovo Magra is Saint Fidelis, celebrated on 7 April. The town's parish church, however, is dedicated to Santa Maria Maddalena: it was built in late Renaissance style in the 17th century on the foundations of an earlier building, and among its finest works keeps a Crucifixion, in the left chapel at the head of the nave, by the Flemish painter Pieter Brueghel the Younger, possibly a copy of a same-titled panel painted by his father Pieter Bruegel the Elder.
Beside the parish church stands the Oratorio dei Rossi, or of the Holy Sacrament, which keeps on its high altar a crucifix that local tradition says was taken by soldiers from Castelnuovo during the ambush of 6 July 1495 on the convoy of Charles VIII of France, near Fornovo. In the old town, in front of the parish church, an open square still serves for town events, while in June the old town hosts Benvenuto Vermentino, a festival dedicated to the area's typical wine.
