This area was populated by Samnites and, after many fierce battles, by the Romans. In the location of Omini Morti a necropolis was found consisting of three groups of tombs arranged in files, which dates back to the Samnite-Roman clashes.
The name Saracinisco recalls the presence of groups of Saracens who had retired to the territory after the defeat suffered against Pope John X in 915 AD.
To defend themselves from menacing Arab presence, according to accounts of Marsio one of the monks of Monte Cassino, to whom the town belonged for a long time, they built a castle.
During the thirteenth century it became the property of the various lords who ruled the Comino Valley and in particular Alvito. The wars between the Angevin and Aragonese during the fifteenth century resulted in the disappearance of some settlements in the area.
While in the Middle Ages there was a branched ecclesiastical organization, by the eighteenth century San Biagio could only count on a priest sent periodically by the abbot of Montecassino.
The name comes from the San Biagio church dedicated to the saint.