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 the Army of Condé in the campaigns of 1792 and 1793 and then served as chief of staff in the civil war in lower Anjou (1794-1796). 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.
When Junot invaded Portugal in 1807, Bourmont offered him his services and was employed as chief of staff of a division. Arrested when reentring France in 1809, he was released upon the intercession of Junot and employed in the Imperial army.
He served in Italy and on the staff of the Eugène de Beauharnais during the Russian campaign of 1812. Taken prisoner during the retreat from Moscow, he managed to escape and rejoin the French army. After the Battle of Lützen in 1813 he was promoted to general of brigade, he took part in the Battle of Leipzig and in 1814 he was promoted to general of division for defending Nogent-sur-Seine.
After the fall of Napoleon, Bourmont rallied to the Bourbons and commanded under Michel Ney on Napoleon's return from Elba. Given his royalist leanings, Napoléon was reluctant to employ him but at the urgent request of Count Gérard, commander of IV Corps, he was given a divisional command in the Army of the North but on the eve of Waterloo he deserted to Louis XVIII, and gave evidence against Ney to his execution. After the Second Restoration, he was given command of the 16th infantry division in Besançon and took part in the Spanish campaign of 1823.
King Charles X of France made him minister of war in 1829 and Marshal of France in 1830. He was commanding the expedition against Algiers when the July Revolution broke out in 1830 upon which Bourmont refused allegiance to Louis Philippe on his accession, and was dismissed from service.
In 1832 Marshal Bourmont took part in the rising of the duchesse de Berry and on its failure fled to Portugal. He commanded the army of Dom Miguel during the Liberal Wars and after the victory of the constitutional party he retired to Rome. At the amnesty of 1840 he returned to France, where he died in 1846.