On the eve of the French Revolution, Bourmont entered the Gardes Françaises of the French Royal Army but he emigrated in 1789. Bourmont served in Louis Joseph de Bourbon, Prince de Condé royalist army in the campaigns of 1792 and 1793. Then he served as chief of staff in the civil war in lower Anjou from 1794 to 1796. After fleeing to Switzerland in 1796, he took part in another insurrection from 1798-1800. He was arrested in 1801 because of involvement with Georges Cadoudal, but three years later he managed to escape to Portugal.