On the accession of Louis XVI Denon was transferred to Sweden; but he returned, after a brief interval, to Paris with the ambassador M. de Vergennes, who had been appointed foreign minister. In 1775 Denon was sent on a special mission to Switzerland, and took the opportunity of visiting Voltaire at Ferney. He made a portrait of the philosopher, which was engraved and published on his return to Paris. His next diplomatic appointment was to Naples, where he spent seven years, first as secretary to the embassy and afterwards as chargé d'affaires. He devoted this period to a careful study of the monuments of ancient art, collecting many specimens and making drawings of others. He also perfected himself in etching and mezzotinto engraving. While in Naples he met Sir William and Lady Hamilton and he etched Lady Hamilton 'posing'.
The death of his patron, M. de Vergennes, in 1787, led to his recall, and the rest of his life was given mainly to artistic pursuits. On his return to Paris he was admitted a member of the Académie de peinture et de sculpture (1787). After a brief interval he returned to Italy, living chiefly at Venice. He also visited Florence and Bologna, and afterwards went to Switzerland. While there he heard that his property had been confiscated, and his name placed on the list of the proscribed, and with characteristic courage he resolved at once to return to Paris: his situation was critical, but he was spared, thanks to the friendship of the painter David, who obtained for him a commission to furnish designs for republican costumes. When the Revolution was over, Denon was one of the band of eminent men who frequented the house of Madame de Beauharnais. Here he met Bonaparte, to whose fortunes he wisely attached himself. At Bonaparte's invitation he joined the expedition to Egypt, and thus found the opportunity of gathering the materials for his most important literary and artistic work. He accompanied General Desaix to Upper Egypt, and made numerous sketches of the monuments of ancient art, sometimes under the very fire of the enemy. The results were published in his Voyage dans la basse et la haute Egypte (Journey in Lower and Upper Egypt), published as two volumes in 1802, a work which crowned his reputation both as an archaeologist and as an artist.
In 1804 he was appointed by Napoleon to the important office of director-general of museums and head of the new Musée Napoléon, which he filled until the Allied occupation of Paris in 1814, when he had to retire. He was a devoted servant of Napoleon, on whose behalf he personally looted vast numbers of works of art in Italy, the Low Countries and Germany and, through agents (including Goya), in Spain, for the Musee Napoleon in Paris. Many of these remain in the Louvre, and elsewhere in France, today. In particular, Denon was one of the very first men to appreciate the importance of the Italian 'primitives'. The majority of those now in the Louvre were looted by Denon during a sweep he made through Italy in 1812. They were publicly paraded, with elephants and other wild animals, like a Roman Triumph, through the streets of Paris, before being deposited in the Louvre.
Denon took full opportunity, while working for Napoleon, to assemble for himself an enormous collection of paintings, drawings, prints, books, statuary and objets d'art. This collection was sold at auction over several days after Denon's death.
After his forced retirement in 1814 he began an illustrated history of ancient and modern art, in which he had the cooperation of several skilful engravers. He died at Paris in 1825, leaving the work unfinished. It was published posthumously, with an explanatory text by Amaury Duval, under the title Monuments des arts du dessin chez les peuples tant anciens que modernes, recueillis par Vivant Denon in 1829. Denon was also the author of a erotic novel, Point de lendemain, published in 1777 (in 1812 as a separate work), and of a number of pornographic etchings.