After the fall of the Roman Empire, Saepinum became a Launguebard center with the name of Altilia (from the German alt-teil meaning old part). But the position in the plain made it very vulnerable which explains the movement of the population in the 8th century to a nearby hill where they built the Castellum Saepini while another part returned to the Samnite area of Terravecchia and built "Castrum Vetus" (=Castelvecchio).
In the 11th century AD Sepino was under the Norman County of Bojano. After the 1456 earthquake also the inhabitants of Castelvecchio moved where today Sepino rises. In the 15th century Sepino was a flourishing center, also thanks to bishop Antonius Attilius, then under the de Molisio barons it was also seat of a Tribunal under the Kingdom of the Two Sicilies, and among the ten most important centers in Molise. Then it was under other feudal lords: the Capua-Altavilla and the Carafa family. In 1805 a terrible earthquake destroyed most of the town and the castle.
