In 1808, de Faÿ commanded the cavalry of the Armée du Midi under Marshals Jean-Baptiste Bessières, Claude Victor and Jean de Dieu Soult in the Spanish Peninsular War. He served at the Fall of Madrid, and at the battles of Uclés, Cuenca, Medellín, Talavera, Ocana, Gebora, Albuquerque, Albuera, Usagre, Elvas, being wounded at Villafranca; one of his dispatches was intercepted and deciphered by the British.