Architects in other parts of the world had been leaning in the direction of Art Nouveau even before 1890. One was the American architect Louis Sullivan, the teacher of Frank Lloyd Wright. Sullivan made use of ancient Celtic designs, incorporating them in the decoration of his otherwise functional buildings, such as the Auditorium Building (1889) and the Carson Pirie Scott Department Store, both in Chicago. In Barcelona the Spanish architect Antonio Gaudi was another precursor of Art Nouveau. Employing medieval Spanish traditions, Gaudi, like Sullivan, created a uniquely personal style. He combined typical Spanish materials such as wrought iron and colorful tile with cast concrete to create fantastic structures in an unusual Art Nouveau idiom. Gaudi's plans and structural models for the still uncompleted Church of the Sagrada Familia (Sacred Family), begun in 1883, show his power of invention as an engineer.

Émile Gallé, the French designer of glass and furniture, was following William Morris's precepts before 1880. Inspired by Chinese cameo glass, he created glassware that was to influence Tiffany in the United States. Tiffany achieved an iridescent glass by using unusual chemical techniques; to Americans his name became synonymous with the new styles of 1900. During the 1890s, Arthur Lasenby Liberty's shops in London and Paris were outlets for the modern style. Italians called Art Nouveau Stile Liberty and Stile Floreale. The Germans referred to it as Jugendstil, after the avant-garde art periodical Jugend (Youth). But the present-day label is derived from Maison de l'art nouveau, a shop opened by the dealer Siegfried Bing in 1896.

A rational architectural approach to the style was achieved by Charles Rennie Mackintosh, a Scotsman. His work so impressed Josef Hoffmann and the Viennese Secession (or Sezession) group that they adapted a similar modification of Art Nouveau, and in doing so created a new style that many decades later became known as Art Deco. Hoffmann's Palais Stoclet in Brussels (1905) was a precursor of the French Art Deco style of 1925.

Art Nouveau was out of fashion before World War I had begun. From the 1920s to the 1950s it was considered by critics a moribund, even ugly, style. About 1960, however, a reappraisal began. In reaction to the unimaginative glass-and-steel rectangular architecture of the 1950s, critics began to turn back to the style of 1900 with a very favorable reconsideration. Numerous exhibitions were held, scholarly publications on Art Nouveau began to appear, and prices for Art Nouveau objects soared. Art Nouveau was incorporated in the rebellious psychedelic style of the 1960s and finally achieved its place as a significant style in the history of modern art.