The patron of Piancastagnaio is Saint Philip Neri, celebrated on 26 May in the Church of San Filippo Neri.
Since 1954, on 18 August, the Palio di Piancastagnaio has been held, awarded through a bareback horse race among the town's four contrade: Borgo, Castello, Coro and Voltaia. The town also holds the Rocca Aldobrandesca and the Shrine of the Madonna di San Pietro.