Accoring to tradition, it was in the town of Dofana that Saint Ansano was recognized as martyr, evangelist and patron of Siena at the beginning of the fourth century. A church was constructed on the site of the martyrdom and the body of the saint was held here until 1108 when it was transferred to the cathedral of Siena. The most ancient written record of the "ecclesia sancti Ansani" dates back to 650. An oratory of S. Ansano is noted in the donations made by count Winigis to the Berardenga abbey in the act of its foundation, in 867. By 1504 however, the chapel was almost in ruins and in 1507-08 the Bishop of Arezzo gave permission to restore it. Some nineteenth century scholars suggested that Baldassarre Peruzzi was behind this restoration.
In 1575, it seems that the building was regularly in order. The most recent restoration work to the Oratory of Saint Ansano was carried out in 1931 and in 1980. The chapel, situated a couple of hundred metres from the church and dedicated to the same saint, has an octagonal layout extended on the opposite side to the entrance with a rectangular collection box. An epigraph situated by the collection box mentions the restoration work carried out and the genius of Pietro Lorenzetti.