The patron of Thiesi is Saint Victoria, celebrated on 23 December in the Church of Santa Vittoria.
The town's most important feast, however, is that of the Madonna di Seunis, celebrated on 7, 8 and 9 September at the shrine of the same name, with a striking ceremony on 9 September. Among the other festivals is that of Santu Juanne, also known as the youth festival, held from 20 to 24 June in the town square. The town also holds the Necropoli di Mandra Antine and the Grotta di Monte Majore.