The Baptistery was built in 1846 to the design of Felice Pizzagalli, already involved in the transformation of the church between 1826 and 1840, and is a noteworthy example of Neo-Gothic style.
Hexagonal in shape, it is composed of spiral columns supported by lions and connected by trefoil arches with spires beside them; tympanums overhead have allegorical statues on top. It is completed with a cone decorated in Gothic motifs and St. John the Baptist, baptising Jesus, on top.
The baptismal font has two different levels. The hexagonal bowl, surrounded by pointed, polylobate arches stands on a hexagonal shaft with six recesses, three of which present Adam and Eve at the front, Moses on the side to the right, and Moses with the Tablets of the Law, to the left. Over the bowl there is a gilded, hexagonal metal ciborium with spired pilasters inlaid with floral motifs and a dome surmounted by the Lamb of God.