Etienne Moreau-Nélaton's family's art collecting began with his grandfather Adolphe Moreau (1800-59). As a stockbroker he possessed ample capital with which to buy the work of artists with whom he was personally acquainted, including Eugène Delacroix and Alexandre-Gabriel Decamps. Moreau-Nélaton's father, who was also named Adolphe Moureau (1827-82), was a high government official and led the railroad company Chemins de fer de l'Est. In 1856 he married the ceramic artist Camille Nélaton (1840–97), with whom he further expanded the family's collection.
After an 1882 visit to the École Normale Supérieure, Moreau-Nélaton decided to become a painter. He began his artistic education by studying with the artists Henri-Joseph Harpignies and Albert Maignan, who were friends of the family. In 1885 he exhibited for the first time in the Salon de Paris. His painting style was influenced by Édouard Manet and Berthe Morisot. Domestic family scenes were his primary subject matter, but he also painted several landscapes. Some of his works are now in the collection of the Musée d’Orsay.
Despite his artistic output, Moreau-Nélaton was perhaps more important as a collector and patron. He first expanded his family's collection to include paintings by Jean-Baptiste Camille Corot, Narcisse Virgilio Díaz de la Peña, Constant Troyon, Théodore Géricault, Thomas Couture, Honoré Daumier and Charles-François Daubigny. Works by Henri Fantin-Latour followed, including Hommage à Delacroix. Moreau-Nélaton also belonged to the group of subscribers who secured and purchased Manet's Olympia for the nation of France in 1890. His collection of impressionist painting was especially impressive, with 10 works by Claude Monet alone, including the well-known Poppyfield at Argenteuil. It also included 7 works by Alfred Sisley, 2 works by Camille Pissarro, and 5 works by Édouard Manet, including The Luncheon on the Grass.