The patron saint of Mignanego is Saint John the Baptist, celebrated on 24 June. The parish church of Sant'Ambrogio, in the main village, is mentioned in a document from 31 March 1210, and in the 13th century the two rectories of Fumeri and Paveto were joined to its pieve.
Among the town's most important historical events is the battle fought on 10 May 1625 at the Pertuso pass, which saw the victory of local volunteer militias, led by the parish priest of Montanesi, over the army of Duke Charles Emmanuel I of Savoy: in thanks for the outcome of the battle, the sanctuary of Nostra Signora della Vittoria was erected. The area was again a theatre of fighting in 1746-1747, during the War of the Austrian Succession, and again in 1800, when French troops were defeated by the Austrian general Hohenzollern. From the second half of the 19th century, the Polcevera valley experienced strong industrial development, with the Brignola firm settling in Mignanego to produce white lead.
