Although many purport to be able to trace their origins in Picinisco to circa 290 BC, it must be said that the first time that Picinisco was documented was in the year 1017. In this year in fact the brothers Pandolfo III and Pandolfo IV, princes of Capua, donated the monastery of San Valentino, sited in the borders of the County and Municipality in the territory of “Pilzinisci” (Picinisco) to the Monastery of Montecassino.
In another document in the year of 1110, relating to the diocese of Sora, with three flour mills in the River Melfa, it mentions the Church of Santa Maria of Picinisco “Ecclesiam Sanctae Mariae de Picinisci”.
In the year 1140, in a “strumento” a document of Ruggero II relating to the borders of the lands of Atina, appear the words “Terra Sanctae Mariae de Piceno”.
In the year 1150, the Norman Ruggero II D’Alta Villa, king of Sicily between 1130 and 1154, conquered the whole Valle di Comino and handed the whole territory to Count Francesco d’Aquino. From then on Picinisco became part of the Reign of the Two Sicilies until 1860 (Spedizione dei Mille 5/5-26th October 1860).
The “Risorgimento”, in fact, gave birth even in the Valle di Comino a liberal movement which brought about the end of the reign of the Bourbons when Garibaldi, on the 7th day of September 1860 entered triumphant in the city of Naples.
The next day a temporary government was formed governing Sora and its surrounding towns of which Picinisco was one, being part of the province of Terra di Lavoro, which later became Caserta.
In 1927 Picinisco passed into the jurisdiction of Frosinone, becoming once again part of Lazio as it had been in ancient times.