Hansen founded his art collection when he acquired his first artworks in 1892. It was initially exclusively focused on 19th century Danish art. Later on, partly assisted by
Théodore Duret, he also began to collect French art, benefitting from the favourable situation on the French art market during
World War I. In 1918, Wilhelm Hansen together with fellow collector Herman Heilbuth (1861–1945) and art dealers Winkel & Magnussen, founded a consortium which was of great importance to the French purchases. Their declared goal was "to Buy and sell works of art with the purpose of bringing good and outstanding art to Scandinavia". For this reason they bought several collections "en bloc" in Paris. In 1918, Hansen founded the French Art Society (Fransk kunst) with the aim of widening the knowledge of French art in Denmark. It arranged a number of exhibitions, culminating with its 1928 exhibition of 19th-century French art in the Ny Carlsberg Glyptotek in 1928, presenting a number of the Louvre's best works, and its exhibition of 18th-century French art at the
Charlottenborg Exhibition Building. He was also president of
Kunstforeningen from 1920 to 1925. He charged Gotfred Tvede with designing a museum building on the Ordrupgaard estate. He opened it to the public in 1918 but closed it again after the sale of part of the collection to the Ny Carlsberg Glyptotek. ==Personal life==