The descendant of a noble family, Malet had his first military experience with the king's musketeers in 1771; when the Revolution broke out, he enthusiastically supported it, though he was disinherited for his open apostasy. He joined the Revolutionary army in 1791 and was aide-de-camp to General Charles de Hesse, serving on the Rhine. His military career for the next eight years was uneventful, but in August 1799 he was sent to defend the Little St. Bernard Pass in southeastern France and was promoted to the rank of brigadier general for distinguished service.

An ardent republican, Malet accepted Napoleon's proclamation of the empire in May 1804 with great reluctance. After 1805 he served in Italy but was cashiered in May 1808 for dealing on the black market. The following year he was imprisoned in Paris on suspicion of belonging to an anti-Bonapartist secret society, the Philadelphes. From July 1810 he was kept under house arrest in Paris, but he escaped on the night of October 22–23, 1812. Assuming the identity of “Général Lamotte,” he went to the barracks of the Second Paris Guard and proclaimed that Napoleon had died in Russia and that he had been named commandant of Paris by a “provisional government.” The Guards believed him, and he was able to secure the release from prison of two prorepublican generals and to shoot the governor of Paris before being arrested.

A few days later Malet was court-martialed and shot. His conspiracy, which came very close to success, deeply disturbed Napoleon, who hastened his return from Russia.