The arch-presbyterial church of Santo Stefano is the most important place of worship in Castel Frentano. The church is dedicated to Santo Stefano, the first martyr to have given his life to spread the faith in Christ and the Gospel. The foundation of the church dates back to the period between the end of the 14th century and the beginning of the 15th centuries, an era in which Castelfrentano became a significant population centre in the area. According to some studies, the building already existed in 1561 when a notary’s document mentions the restoration of its façade. In the first half of the 1600s another restoration was carried out and during the 1700s as can be read on an inscription at the entrance, the church was completely reconstructed and then reopened for worship on 1780.In 1980 further restoration work was carried out by the superintendence for Architectural Heritage of Abruzzo. The single nave building, with side chapels has a façade constructed in bricks and divided horizontally into two parts. There is a stone entrance from the late baroque period, which has a corresponding rectangular window above. The façade is completed by a tympanum and there is a bell tower located on the neighbouring structure that has a square design and is divided into three parts with cornicing at each level. The church has a single nave structure with side chapels, a transept and a domed roof. The apse behind the main altar is made of polychrome marble is surrounded by a marble balustrade. The decorations are created with plaster, the baptism font, probably dating back to the 16th century is made of wood, not to be missed is the magnificent organ, the work of Quirico Gennari of Lanciano, that is now housed in the cantoria.