The interior has three aisles: the central nave is taller and twice as wide as the side aisles. The entrance portal – its architrave supporting a copper Saint Michael the Archangel by Carlo Anzini – leads into a vestibule with a barrel vault. This vault supports an elevated, square chamber that opens into the central nave via a tall window.

The axial lines of the vestibule’s spine walls continue into the church as two rows of piers and columns; six round arches on each side divide the aisles.

The columns (three on each side) vary considerably in form and size. They feature an octagonal section and inverted truncated-pyramidal capitals in a Byzantine-Ravenna style. Their varied adjustments to their bases strongly suggest they were reused elements from earlier structures.

Beyond the vestibule, on the left, is the baptismal font: an octagonal sandstone basin decorated with Gothic arcading. On the right, past the holy-water stoup (two very ancient elements – pillar and basin), stands a small altar topped by an 18th-century canvas of Saint Michael the Archangel. The confessional is also located in this corner.

Along the walls of the side aisles hang terracotta Stations of the Cross made in 1962 by the artist Donatella Marchini. Two modern statues (a Christ and a Madonna) are set in the niches created by sealing the two side doors, which feature the decorated lunettes visible from the exterior. Several paintings belonging to the church are preserved in the rectory.