The patron saint of Trezzo sull'Adda is Saint Cajetan, celebrated on 7 August.
In the hamlet of Concesa, the local patronal feast called «FestAssunta» is held on the second Sunday of September. The town feast (Sagra cittadina), instead, is held in October and culminates on the first Sunday of the month. The town holds the Visconti bridge of Trezzo and the Crivelli picture gallery, as well as the Sanctuary of the Divine Motherhood of Mary.