[4] Kröller-Müller also collected works by modern artists, such as Picasso, Georges Braque, Jean Metzinger, Albert Gleizes, Fernand Léger, Diego Rivera, Juan Gris, Piet Mondrian, Gino Severini, Joseph Csaky, Auguste Herbin, Georges Valmier, María Blanchard, Léopold Survage and Tobeen.

However, Bremmer advised her not to buy A Sunday Afternoon on the Island of La Grande Jatte by Georges Seurat, which turned out to be an important icon of 20th-century art.

[3] From 1913 onwards parts of her collection were open to the public; until the mid-1930s her exhibition hall in The Hague was one of the very rare places where one could see more than a few works of modern art.

In 1935, they donated to the Dutch people their entire collection totaling approximately 12,000 objects, on condition that a large museum be built in the gardens of her park.

A lavish art gallery was planned near their iconic lakeside Jachthuis Sint Hubertus hunting lodge and landscape statue of their close personal friend, the South African Boer General Christian de Wet on the estate.