The patrons of Castronno are Saints Nazarius and Celsus, celebrated on 27 July in the Church of Santi Nazario e Celso.
In 2026 Castronno became known as the site of Italy's first geocaching Mega-Event, which drew more than a thousand people to the town's Area Feste from across Europe and even the United States. The town also holds the Church of Sant'Alessandro and Monte Roncaccio.