The parish church of Bosses, dedicated to St. Leonard, located near the castle, dates from 1861-1862 and was built, on the remains of the old chapel of St. Leonard, in the neo-Gothic style. It is one of the earliest examples of neo-Gothic architecture in the Aosta Valley.

The walls are decorated with frescoes painted in 1862 by Ivrea painter Giuseppe Stornone. Also of special value is the 18th-century carved and gilded altar placed in the right side chapel.