Bry's name comes from the Celtic word Briw, which means a bridge or a river crossing. The area has been inhabited since Neolithic times. The town's motto, which features on its coat of arms, is "Moult viel que Paris" - old French for "Much older than Paris".
In 1903, archeologist Adrien Mentienne uncovered the bones of a large bovine which died 15,000 years ago. In 1982, the skeleton of a woman who died in the 5th century BC was uncovered beneath the playground of a school in Bry. It is now housed in the town's museum.
From that century onwards, there was a permanent human presence where Bry now stands. In 1886, a necropolis was found which contained pottery, Gaul and Frankish weaponry, silver and gold jewelry, and coins, dating from the Gaul era to the Merovingian. The first known written mention of the town named Bry was in a charter signed by King Charles the Bald in 861.
In 1404, Robert de Châtillon, cousin of King Charles VI, was Bry's feudal lord. His castle no longer stands, and its exact location is uncertain. Bry's current château was built in the 1690s. It became the town hall in 1866. It was rebuilt after the Franco-Prussian War of 1870.
The railway came to Bry in 1926, followed by the motorway (1970) and the RER (1977). The town's hospital was built in 1936.
Bry's most treasured artwork is a diorama painted by Louis Daguerre. The painting changes as each day wears on, mimicking daylight and night-time; the painted candlesticks light up at night. It is kept in the local church.