The church was erected following the establishment of a Benedictine priory in the 11th century. Enlarged and remodeled numerous times, it nevertheless retains a certain unity. The nave, transept, and apse date from the 12th century and are in the Romanesque style. The side aisles were added at the end of the 12th century. Later, in the 15th century, an additional bay of the nave was built. As for the side chapels, pierced with Gothic windows and supported by powerful buttresses, they were added in the 15th and 19th centuries. Listed as a Historic Monument since 1862, built of noble materials (ashlar), the building has the dual distinction of being roofed by stone slabs and having two bell towers: one is octagonal and notably pierced with ogival bays, the other is a bell tower-arcade type with three bell bays. The three bays of the exterior side portal are richly decorated with arches and capitals adorned with flowers, petals, and sculpted figurines. They present a balanced composition of small columns and semicircular arches. Architecturally, note the sculpted modillions of the cornices overlooking the chevet and transept, as well as the elaborate decoration of the "south" portal, where Gothic elements coexist with Romanesque ornamentation (bas-reliefs depicting figures and interlacing). The west portal is decorated with elegant columns from the 13th and 14th centuries.
Inside, admirable coffers painted with rosettes adorn the ceiling, and a magnificent 16th-century organ case sits on an entire wall. This organ case, equipped with an Italianate case dating from 1506, was restored in the 18th century and in 1966, following its listing by the Fine Arts Museum. It has also been undergoing a new restoration since November 2007, which was completed in July 2009, the date of its new commissioning.
Accompanied by background music, lighting in several stages, and a constantly renewed decor, the Valréas nativity scene, one of the most renowned in Provence, occupies the Notre Dame-de-Nazareth church from Christmas to Candlemas. Covering 57 m², beautiful and very old figurines (some of which are centuries old) make their way towards the Infant Jesus.
The church and its Place Pie serve as the backdrop each year for the feast of the Night of Little Saint John on June 23.