On 19 August Castelmagno celebrates the very ancient feast of San Magno. The sanctuary of San Magno, dedicated to the cult of San Magno the martyr, protector of livestock and pastures (the main sources of livelihood for the local people), stands at 1,761 metres above sea level along the road that climbs to the Colle Fauniera: it is normally open from June to September, with overnight and refreshment services for pilgrims, and the feast of the saint and of the sanctuary falls on 19 August.
Castelmagno is part of the historical Occitan linguistic area, the reason for several celebrations during the year, such as the traditional San Jouan Muzico in July and the Ferragosto concert by Lou Dalfin. The municipality also holds the Chiesa di Santa Maria Assunta, Sant'Anna, Sant'Ambrogio and Casa Narbona.
