The current building, a national monument, is the result of an interesting overlapping of extensions from different eras. The first testimony of the church is in a document from the early 11th century. where a "cappellam" donated to the canons of s. Maria di Novara da Gualberto, bishop of Novara from 1032 to 1039. The chapel, dedicated to S. Gaudenzio, first bishop of Novara (337-417), had a rectangular plan and occupied the area of the present presbytery.

The first extension is located between the 12th and 13th centuries. As there was not enough space, the orientation was changed, north-south, building that part that today is the central nave (including the two aisles) and the Romanesque façade between the two pilasters.