The patron of Castel Frentano is Saint Stephen the Protomartyr, and his patronal feast is celebrated on 3 August in the Church of Santo Stefano.
Inside, the church holds frescoes by Vincenzo Ronzi da Penne and the vestments used for the traditional Good Friday procession. The town also holds the Church of Santa Maria della Selva and the Teatro Comunale di Loreto Liberati.