The patron of Cologno al Serio is the Assumption of Mary, celebrated on 15 August in the Church of Santa Maria Assunta.
In 1452, Francesco Sforza Visconti, fourth Duke of Milan, made his knight, the nobleman Sagramoro II Visconti, castellan of the Rocca of Cologno al Serio. The town still holds Porta Rocca, Porta Moringhello, Porta Gnano and Porta Cassatiga today.