He entered the civil service in 1762; two years later he bought the office of master of requests, and in 1766 further advanced his position by a rich marriage.

His first book was the fictitious Mémoires d'Anne de Gonzague, princesse palatine (1786), thought by many people at the time to be genuine.

[1] Sénac witnessed the beginnings of the French Revolution in Paris, but emigrated in 1790, making his way first to London, and then, in 1791, to Aachen, where he met Pierre Alexandre de Tilly, who asserts in his Memoirs that Sénac attributed the misfortunes of Louis XVI to the refusal of his own services.

In 1793, while his recollections of the Revolution were still fresh, he wrote a novel, L'Émigré (Hamburg, 4 vols., 1797), which shows perspicacity and good judgment in its treatment of events.

[2] Sénac also wrote a moderate exposition of the causes that led to the Revolution, entitled Du gouvernement, des mœurs et des conditions en France avant la Révolution, avec les caractères des principaux personnages du règne de Louis XVI; the last part was reprinted (1813) by the duc de Levis with a notice of the author as Portraits & caractères.