The patron saint of Castelgrande is Saint Vitus, celebrated on 5 July. His cult in the town is documented as early as the 17th century: by decree of 17 September 1632, the Bishop of Muro, Clemente Confetti, granted Berardino De Santo, who had established a lay chaplaincy dedicated to Saint Anthony, Saint Vitus and Saint Lucy, the right of patronage, limited to the male line, together with the right of burial in the church of San Bernardino, dedicated from then on to Saint Anthony of Padua.
Castelgrande also venerates the Virgin Mary of Constantinople, celebrated every year with a solemn procession on the Tuesday after Pentecost, and the Assumption, on 15 August. The town, whose humanist-era name was Castrum magnum, appears in a 16th-century depiction as a group of houses around a rectangular-plan church: a detail which, together with the record that in 1446 Castelgrande was the only settlement in the area taxed for the clergy's concubines, suggests a once more numerous ecclesiastical presence than elsewhere.
