The current Parish Church, dating back to the mid-13th century, was built on the original Early Medieval Church, whose construction dates back to around the year 1000, the time of settlement of the fortified village of Castelpetroso.
The original building, built outside the first city wall at a significantly lower elevation than the later one, was smaller than the current one. The perimeter wall, discovered during restoration work in the last century, remains intact. The presence of several Roman-era stone elements reused in the construction of the bell tower suggests the former existence of a place of worship.The bell tower, built between 1545 and 1606, is composed of numerous recovered elements dating from the Roman to the Middle Ages. Of particular importance is the plaque at its base, which certifies the presence of the Tromentina Tribe, which occupied the area after the Third Samnite War. At the top of the bell tower are a contemporary ciborium and two 16th-century bells, housed within a structure created from elements of the 13th-century portal.
The three-nave church, dating back to the 18th century, withstood the earthquake of July 26, 1805. Inside, there are 16th- and 17th-century altars: the Altar of the "Cappellone," with the early 18th-century statue of Our Lady of Sorrows by Giacomo Colombo; the Altar of the Deposition, with a canvas from the Solimena school; the Altar of the Rosary with the 17th-century statue of the Madonna; the Altar of the Conception; and the Altar of Saint Anthony, probably the oldest. In the center of the nave is the High Altar of Saint Martin, to whom the church is dedicated.
The 17th-century walnut pulpit and confessional in the right aisle are particularly noteworthy.
