The existence of Montbellet is attested as early as 850. The parish church was originally part of a priory dependent on the abbey of Saint Claude in the Jura and which had as an annex the chapel of Saint Oyen, a Jura saint. Inside, three construction stages can be observed, according to R. Oursel:
1/ From the Romanesque period, in the 12th century, remains the bay under the bell tower with octagonal dome on trunks, carried on two lateral arches that allow the passage from the rectangular plan to the square plan
2/ The Gothic period: the choir, from the end of the 13th century or the beginning of the 14th century, with a flat chevet, is two bays deep, it is vaulted with chamfered arches, separated by a strong double arch with a slightly broken arch. It is lit in the axis by a large window with a gothic filling with two lancets, set with visible stones that stand out against the wine-red chevet. The blue stained glass windows in the choir are modern. The square side chapels with ribbed vaults on corner brackets are also from the 13th century. A hagioscope (rectangular day, hollowed out at an angle) allows a view of the high altar from the south chapel. The liturgical pool in the south, under an arcade and spandrels with openwork rosettes, contributes to the dating of this medieval part
3 / Early eighteenth century: the single rectangular nave ceiling does not appear Romanesque, it was expanded in 1702. Built on a sloping floor, it has a fairly steep slope from west to east: 3 steps and 5 steps from the porch lead to the first third of the nave; benches are installed on the last three steps, which gives a view down to the choir. The nave opens on the west side with a semicircular door with chamfered edges, and on the south side with a secondary semicircular door with two Tuscan imposts and a keystone engraved with the inscription: DOMUS MEA DOMUS ORATIONIS ("My house is a house of prayer").
Restoration work continued in the 19th and 20th centuries.