 Cadro is first mentioned in 735 as "Cadelo".Under the Lombards kings, Cadro was mentioned in connection with the Totoniden from Campione d'Italia as a Vicus in 854.Some of the major landholders during the Middle Ages included the monastery of S. Ambrogio in Milan, the Benedictine monastery of S. Abbondio in Como and the Hospital of S. Maria in Lugano.