Mignano Monte Lungo borders the following municipalities: Conca della Campania, Galluccio, Presenzano, Rocca d'Evandro, San Pietro Infine, San Vittore del Lazio, Sesto Campano, Venafro.

The first settlers in the area were the Sidicini; the Etruscans founded here the town of Cesennia, which later passed under Roman control.

In 1581 his heir Ettore Leognano Fieramosca ceded it to Giulio Cesare De Capua.

In 1734 the troops of Charles of Bourbon besieged here Marshal von Traun, who had to flee to Capua.

During World War II Mignano was the seat of fierce fightings, part of the Battle of San Pietro Infine.