The patrons of Cosio d'Arroscia are Saints Peter and Paul, and the feast falls on 29 June. The order of the day is the usual one: vespers first, then the procession through the streets of the village, accompanied by the confraternities.
In 2024 the mayor and the mayors of the other municipalities of the upper Arroscia valley walked with the villagers. Outside the built-up area, at Villa, stands the church of San Pietro del Fossato, older than the fourteenth century.
