The patroness of Tiglieto is Our Lady of the Assumption, celebrated on 15 August. The parish church of Saints Bernard and Mary Assumed, in the locality and municipal seat of Casavecchia, was built in 1934: divided into three naves, it holds inside two frescoes by the painter Piero Dalle Ceste.
The town's symbol-monument, however, is the abbey of Santa Maria alla Croce, complete with a monastery and adjoining Romanesque church: built by Cistercian monks over the course of 1120, it was one of the first religious buildings raised in Liguria and Italy, completed with a large cloister and the convent. Known simply as the «badia di Tiglieto», it was the municipality's main settlement until the 1920s. Near the valley floor of the Orba torrent stands an old stone bridge with five unequal arches, the central one twenty metres high, built by the same Cistercian monks and later restored in the 17th century by the Raggio marquises. In February 1747 the town suffered, like the Republic of Genoa its ally, the invasion of the Austrians, who besieged the local church before being driven back by Genoese soldiers sent from Genoa on 11 March.
