The Romans had built in the territory of present-day Pozzilli an aqueduct collecting the waters of the Volturno river, and the name Pozzilli probably derives from the presence of small wells (pozzilli) connected to the Venafro aqueduct. Pozzilli was founded only some centuries ago, much later than its frazione Santa Maria Oliveto, going back to 839 AD, when the abbot Castel San Vincenzo sent here a colony from the Valva area (near Sulmona) to build a hamlet on the hill around the church of San Lorenzo. In 1234 the fiefdom was under Ruggiero Galluccio, then passed to Gualtiero d'Aversa, and in the 16th century to the Pandone and finally to the Gaetani family, until 1806.