Saint-Malo-en-l’Isle was founded by Bishop Jean de Chatillon in the 12th century.

Le Rocher, an islet and monastic refuge just off Saint Malo, became a source of rivalry between local dukes and bishops around the 13th century. It was the main stake in a battle between Du Guesclin and Jean de Montfort, an ally of the English, and it was only in 1382 that the town finally became part of France. The Solidor tower was built in an attempt to subdue a divided and riotous population and effectively marked this period of transition.

The town became a thriving commercial port after Jacques Cartier discovered the Saint Lawrence estuary in the 16th century. Trade with Canada grew and Saint-Malo became France’s main trade port.

Saint-Malo’s economy gradually declined in the 18th century, and the town turned to tourism by shifting its structure from industrial centre to seaside resort by building a casino and a grand hotel.
Most of the buildings in the town centre were destroyed by repeated bombings - a number of 18th-century hotel-villas were restored, but most of the city's characteristic half-timbered houses were torn down.