The Church of St. Mary was built in honor of the most important religious settlement existed in Petacciato around the 1150. The Church, originally called Church of St. Rocco, Patron of the city, is located in the historical center and was built between the XI and the XIII century. Both in apses and in walls of bell tower, it is possible to see the characteristics of Romanesque architecture typical of Molise in the 13th century, although it has undergone remarkable transformations over the centuries. In fact, from the structure of the church, it seems that the entrance was later moved to one of the lateral sides.
The Church of St. Mary is made of tuff and sandstone, it has three naves with three altars, including altar of St. Antony with its chapel dedicated to D’Avalos family. The Church has a type of Greek cross plant and it has three apses supported by semi-pillars and semi-columns, characterized by windows that are subsequent church’s construction. The main facade, completely plastered, has a decorated portal with blind arches on the sides and pilasters strip to corners. The use of arches with pilasters, suggests that bell tower, built on a quadrangular base on the left side of facade, dates back to the second half of 12th century, although two impressed stone bas-reliefs on the main side of the bell tower are of the 11th century.
The bell tower is characterized in its lower part by a base, in central part by four hanging arches, pilasters and anthropomorphic elements. The higher part, more articulated, has a twin-blade, an angular clock and angled pilasters. Specifically, the tower is divided into two sections. In the first there are four arches, with angular and central pilasters, with simple shelves or with heads of animals. The second section, slightly reversed with respect to lower body and separated by a geometric frame of shells and rebars, adds to angular sections, two pillars in center. Right under bell tower there is the Crypt of St. Rocco. A stoup, a wooden statue of St. Joseph in the presbytery, the altar of St. Lucy and the dossal of Addolorata date back to the period between the 17th and 19th century. Of 19th century are the statues of Risen Jesus and St. Rocco, as well as the pulpit in the central nave.