The castle of Casole is recorded from the beginning of the eleventh century as a stronghold of the bishops of Volterra, in a territory disputed by Volterra, Siena and Florence. After the battle of Montaperti, in 1260, it passed under the rule of Siena, and the village was enlarged with new fortifications, taking the street layout it still has today. But the people of Casole did not accept it: many of them, led by Rainerio del Porrina, of a powerful feudal family, opposed the submission, and Porrina remained for centuries, long after his death, one of the best-loved figures of the town. In the collegiate church of Santa Maria Assunta, consecrated in 1161, are the tomb of Beltramo Aringhieri, the work of Marco Romano, and that of bishop Tommaso Andrei, carved by Gano di Fazio in 1303; a museum of sacred art is attached to the church. In the pieve of Mensano the carved capitals of the columns are reckoned among the finest things in the Romanesque sculpture of the Siena area.
In July 1944, at the passage of the front, the village suffered very grave destruction. The hamlet of Monteguidi, on the other hand, is the place where Carlo Cassola set his novel La ragazza di Bube. Seven contrade take part in the palio of Casole, and two of them — Rivellino and Pievalle — were born in 1984 by splitting the old contrada of Casole in two. The territory, largely inside the Montagnola senese, has a border worth telling: with the comune of Pomarance, in the province of Pisa, it shares a stretch forty-five metres long. And in this village of fewer than four thousand people is based the Pramac team, which in 2024 won the MotoGP world title with Jorge Martín.