Considering the title “plébain”, which is traditionally attributed to the parish priest, it is believed that the parish of Morgex is one of the oldest of the upper Aosta Valley. This hypothesis was confirmed by the archaeological digs which brought to light the remains of the ancient early-Christian baptismal church (5th-6th century), while the church of Morgex was mentioned for the first time in the papal bull of Alexander III in 1176.

The medieval church was readjusted on several occasions, until it was given its current appearance with the restoration and extension campaign that got underway in 1687, at the end of which, in 1705, Monsignor d’Arvillars consecrated the building.

The interior decoration is the fruit of the interventions of the Savyoard painter Girollet as far as the vaults of the apsidal area are concerned (18th century), while the other works are due to the painter Lancia, who was active during the first half of the 20th century.
Of particular historical and artistic value is the wooden crucifix dating back to the end of the fourteenth century which dominates the central nave.

All that remains of the ancient decoration of the church is a Last Supper on the left hand side of the central nave, it is dated 1559 and the interesting frescos of the fifteenth century chapel at the bottom of the left hand nave. The main altar is noteworthy, with its rich frieze and gilding, dating back to the beginning of the eighteenth century, although the central painting of the Assumption of Mary was replaced with a painting by Lancia after that a fire destroyed the original one in 1931.