His reputation as a connoisseur, who laid down the principles by which the hands of Italian master drawings could be ascertained, led to him being made an associate, then an honorary (1757) member of the Académie royale de peinture et de sculpture. In 1764-65 he got into a public dispute in the pages of the "Gazette littéraire de l'Europe" with Giovanni Battista Piranesi, whom Mariette admired greatly as an artist, over Piranesi's polemical stand that the magnificence of Roman art derived from its Etruscan roots, rather than from its Greek borrowings   Mariette's circle of friends was large, included Andre-Charles Boulle and was broad enough to define the state of art connoisseurship in France during his time, beginning with the circle he met at the houses of the prodigious collection Pierre-Antoine Crozat, where besides artists like Antoine Watteau and the classicizing sculptor Edmé Bouchardon, Mariette met the abbé de Maroulle and the comte de Caylus, who helped sharpen his eye. Mariette married Angélique-Catherine Doyen in 1724. He acquired a country house at Croissy, which he named "Le Colifichet" was ennobled during the reign of Louis XV, and honored with the Order of the Saint-Esprit. His major ambition was to write a history of engraving and a dictionary of artists. In preparation, he compiled numerous annotations to the "Abecedario pittorico" (1704) of Pellegrino Antonio Orlandi. His father's notes on artists, accumulated in the course of the art trade, and his own wide experience and correspondence among the "cognoscenti", were the basis of these projects, none of which, however, ever came to fruition. Caylus used Mariette's notes on Vasari's "Lives" for his manuscript "Vies d’artistes du XVIIIe siècle". Fortunately a "corpus" of Mariette's assembled materials— pamphlets, manuscripts, salon and exhibition catalogues, including the salon criticism of Diderot—came into the hands of Charles-Nicolas Cochin, an artist and guiding spirit of Neoclassicism, and, greatly augmented, was deposited in 1880 at the Bibliothèque Nationale   Not until 1851 were Mariette's notes and anecdotes entered in the "Abecedario" compiled by Philippe de Chennevières and Anatole de Montaiglon, in the six volumes of "Abecedario de P.J. Mariette et autres notes inédites de cet amateur sur les arts et les artistes" (Paris, 1851–60).