The patron of Castelnuovo Parano is Saint Maurus, celebrated on 15 January.
The town has a distinctive Marian tradition: every three years, on 21 August, the faithful of Ausonia and Castro dei Volsci meet to recall the journey of the Virgin of the Plain, who according to tradition stopped to rest in Castelnuovo Parano itself; on the night of Holy Saturday the "race of the Madonna" also takes place.