Three forest villages (Auderghem, Watermael, and Boitsfort-Bosvoorde), were one for centuries. In 1794, the soldiers of the French Revolution decided to separate these into three distinct municipalities. In 1811, Napoleon decided to reunite the three villages, by imperial decree, into a single administrative entity. But Auderghem was withdrawn from this union by royal act, leaving Watermael-Boitsfort or Watermaal-Bosvoorde on its own. Thus, Auderghem became an independent municipality in 1863, with only 1,600 inhabitants.
With the construction of the rail line linking Brussels and Tervuren as well as, in 1910, the construction of the Boulevard du Souverain or Vorstlaan, modernization came to the municipality and the population grew quickly.
In 1956, Paul Henri Spaak lead the Intergovernmental Conference on the Common Market and Euratom at the Val Duchesse castle in Auderghem, which prepared the Treaties of Rome in 1957 and the foundation of the European Economic Community and Euratom in 1958
