The patron saint of San Giacomo degli Schiavoni is Saint James the Greater, celebrated on 9 August: his bust is depicted on a red field on the municipal coat of arms.
Once the Casale di San Giacomo, the town was repopulated in the first half of the 16th century by a colony of Slavs, known as «Schiavoni», coming from Dalmatia and fleeing Ottoman invasions, called upon to repopulate many areas of Molise devastated by earthquakes and famines. San Giacomo degli Schiavoni was one of the Molise communities, along with Palata, Castelmauro, Tavenna, Mafalda, San Biase and Montelongo, where Molise Croatian was spoken, today surviving only in Acquaviva Collecroce, Montemitro and San Felice del Molise. In 1902 a Waldensian community also arose in the town, founded thanks to itinerant sellers of Holy Scripture and to San Giacomo natives returning from the United States after encountering the evangelical faith there: despite the difficulties it faced, it kept its vitality alive for much of the 20th century.
