The first informations about Montalto date back to the 10th century, when the Monastery of Santa Maria delle Cacce from Pavia extended its possessions in the area. In 1164 it passed with all the Oltrepò area under the control of Pavia, who gave it as a feud to the Belcredi family. The “podesteria o squadra” of Montalto, subject to the Belcredi (who nominated the Podestà, a privilege reserved in other squadras to the city of Pavia), also included Oliva Gessi, Mornico Losana, Torricella Verzate, Lirio and Montù Berchielli (in the municipality of Rocca de’ Giorgi). Also mentioned in the villages of the fief are the now hamlets of Finigeto and Villa Illibardi. Under the power of the Sforza in 1477 Montalto became a fief and county of the Strozzi from Mantua (a branch of the larger Florentine family), even though the Belcredi remained the wealthiest family and still conserved the property of the castle. In 1617 the fief was sold to the Taverna, Counts of Landriano, but in 1658 the Belcredi bought it back, keeping it until the end of feudalism in 1797. In the meantime, the fief became a Marquisate. In the 19th century Montalto became the head of administration in the province of Voghera (division of Voghera in the province of Pavia from 1859). With the unification of Italy it received the new name of Montalto Pavese. In 1939, after the suppression of the municipality of Montù Berchielli (CC F702), part of it, including the former municipal site Cà del Fosso, was added to Montalto.