Lieutenant de vaisseau from 1779, in the siege of Savannah he saved the life of d'Estaing despite being severely wounded himself, for which he was made a knight of Order of Saint Louis.

Major de Vaisseau from 1784, he cooperated in the tasks assigned to M. Choiseuil-Gouffier, ambassador to Constantinople, and was charged with instructing the Ottomans in the arts of fortification, artillery, metallurgy, naval architecture, and so on.

Made capitaine de vaisseau on 1 January 1792, he was promoted as early as the following July to the rank of rear admiral, commanding the French naval forces in the Mediterranean from his flagship Tonnant.

On his return to Toulon in March 1793, he went to Paris, where he got the government to adopt a maritime penal code, that would prevent many future insurrections and mutinies but still provoke much discontent in France's naval bases.

Under pressure from general Hoche, he presented a plan for the 1796 French invasion of Ireland to the Directory, with Morard de Galle commanding the naval forces.

At the time of the ministerial reshuffle in preparation for the coup of 18 Fructidor year V (4 September 1797), he was replaced by Georges-René Pléville De Pelley, but was instead made France's ambassador to Spain.

He composed four reports for the First Consul, proposing a reorganization of the navy and taking a strong position and courageous stand against Napoleon's reimplementation of slavery in French colonies, as Truguet's solid republican convictions made him consider equality as a fundamental right.

He was probably the only official to dare oppose Napoleon on this point, and was violently attacked and mocked by those favoring a return to the old order in the colonies and strongly reprimanded by the First Consul.

In 1804, while all were conscientiously signing a "spontaneous" petition amidst his whole fleet to demand an imperial crown for Napoleon, in the same way as was being done in the army, Truguet publicly took a stand against the establishment of the Empire in a letter that became historic.

Admiral Truguet returned to Paris where Louis XVIII brought him back into the navy at the head of the naval corps, and made him a knight grand-cross of the Légion d'honneur.