In 933 Avranches and its territory, the Avranchin, were ceded to the Normans.
In 1172 (September 27-28) a council was held at Avranches apropos of the troubles caused in the English Church by the murder of the Anglo-Norman saint Thomas Becket. Henry II, King of England, after due penance done in Avranches on May 21, 1172, was absolved from the censures incurred by the assassination of the holy prelate, and reached the Compromise of Avranches with the Church, swearing fidelity to Pope Alexander III in the person of the papal legate.
It was forbidden by the same council to confer on children benefice carrying with it the cure of souls, or on the children of priests the churches of their fathers. Each parish was required to have an assistant (vicarius) and the Advent fast was commended to all who could observe it, especially to ecclesiastics.
In 1978, Saint-Pair-sur-Mer split from Jullouville.
In 1979, Genêts and Saint-Jean-le-Thomas split from Dragey-Tombelaine which changed its name to Dragey-Ronthon.
In 2000, Carolles split from Jullouville and became a commune again.
Saint-Michel-des-Loups which had 477 inhabitants became a part of the canton of Sartilly.
The town was founded on high ground overlooking the dunes and coastal marshes along the bay forming the corner between the peninsulas of the Cotentin and Brittany. From Avranches, it is possible to see the Mont Saint Michel, which was founded by Saint Aubert, Bishop of Avranches in the 8th century.
A museum houses the collection of manuscripts of Mont Saint Michel, deposited in the municipal archives during the French Revolution. It is one of the largest collections of medieval illuminated manuscripts in France, outside national and university libraries.
Formerly dominated by the cathedral, where Henry II did penance, an open grassed area La Plate-Forme overlooking the bay towards Mont Saint Michel displays only a few remnants of the destroyed building.
The major church Notre Dame des Champs was constructed in Gothic Revival style in the 19th century to restore the religious life of the town after the destruction of the cathedral. A smaller church Saint Gervais houses a treasury, best known for the purported skull of Saint Aubert complete with hole where the archangel Michael's finger pierced it (probably a prehistoric trepanned skull).
The botanical gardens were founded in the grounds of the former Franciscan convent in the late 18th century. The expansion and introduction of exotic species in the 19th century and the location of the gardens overlooking the bay made the gardens an important sight in the town.
The Manoir de Brion, an ancient Benedictine priory of Mont Saint Michel, is located in Dragey.