She volunteered as a nurse in the French Red Cross and saw how badly the financial situation had become for many of the artists of Paris who were already struggling.
Because many of her artist acquaintances frequently had little or nothing to eat, in 1915, she opened the canteen that provided a full meal and a glass of wine for only a few centimes.
While her canteen provided a valuable service, during the war it became a popular gathering place for the artistic community.
During the war a government curfew was put into place.
As a result, soon her place became crowded and at night, filled with music and dancing.
In January 1917, Georges Braque, who had been wounded fighting in World War I, was released from military service.
Marie Vassilieff and Max Jacob decided to organize a dinner for Braque and his wife, Marcelle.
Among the guests was Alfredo Pina with his new companion, Beatrice Hastings, who had recently ended her two-year relationship with Amedeo Modigliani.
Knowing Modigliani's penchant for causing a disturbance when he drank, and that he drank often, Marie Vassilieff did not invite Modigliani to Braque's party.
The art community was small, however, and word of the get-together soon reached Modigliani.
An uninvited, and very drunk, Modigliani showed up, looking for a fight.
A scuffle ensued, a pistol appeared, and Marie Vassilieff, all five feet of her, pushed Modigliani downstairs while Pablo Picasso and Manuel Ortiz de Zarate locked the door.
Marie Vassilieff made what is now a very famous drawing depicting the events of the evening.
Marie Vassilieff's own artwork is primarily in the Cubist style, her most interesting paintings are portraits of dancers as well as those of her friends, Jean Cocteau, Picasso, and Matisse.
Known, too, for her decorative furniture pieces and her doll-portraits, Vassilieff's works remain very popular.
Although her works never gained the lofty stature or astounding prices of some of her renowned contemporaries, today they may be found in museums and private collections worldwide.
As both an artist and friend, Marie Vassilieff was an integral part of the great creative community of Montparnasse, where today one may still see her ornamental panels, created in 1927 for the pillars in the dining room of the La Coupole.
After several exhibitions in London in 1928 and 1930, and in Italy in 1929, she opened the Vassilieff Museum.