Before the fourteenth century, the territory of Castel d'Aiano was included in the parish of S. Nicolò di Villa d'Aiano and had only one oratory, or chapel, dedicated to St. Maria Assunta. After 1330 the ancient chapel, crumbling, was demolished and a new church dedicated to the Assumption of Mary was built on the same site, consecrated in 1338.
In 1615 the church, in need of restoration, passed from the popular patronage to the Bishop of Modena with the understanding that the latter would have to provide for the restoration, in exchange for the transfer of the right. The agreement was honoured, and the bishop of Modena provided for the restoration of the extent of which, however, is not known; the bell tower was built at the same time.
The church of Santa Maria Assunta stands in the centre of the town of Castel d'Aiano, along the SP 623 which runs along the ridge between the valleys of the Reno and the Panaro. The gabled façade is characterized by a deep arch which acts as a narthex and by an exposed stone facing which is repeated along the lower register of the sides and of the presbytery area, in contrast with the vertical thrust of the plastered walls of the central nave.
The interior, with three naves, is paved in Palladian stone, has plastered walls and is covered with a flat ceiling with lowered exposed concrete beams. The presbytery is closed by a semi-circular apse.