Her parents were Wladimir Filatoff, a Russian minor nobleman, and Marine Guelariev, whose father was Polish and whose mother, Adeline Louvier de Balmont, was French.

They studied together during the school year 1902–1903 at the École pratique des hautes études, section of philological and historical sciences.

[2] Before the First World War, Nathalie Demassieux began a thesis on the equilibrium between halogenated lead salts and alkali metals in the laboratory of Léon Ouvrard.

After his death during the war, she finished her thesis under the direction of Professor Henry Louis Le Chatelier, chair of general chemistry at the Sorbonne.

[9] In 1930, Demassieux obtained a position as a lecturer at the Faculty of Sciences of the University of Caen, becoming only the third woman to obtain a position as a lecturer at a French university, after the chemists Irène Joliot-Curie (Nobel Prize winner) and Pauline Ramart (who rose to become chair of organic chemistry at the Faculty of Sciences of Paris from 1935 to her death in 1953).

[2] Concerned with popularization and feminism, she gave lectures, such as the one on Louis Pasteur given in 1923 during the general assembly of the League for Women's Rights.

During the 1939–1945 war, she turned to practical applications by registering patents on phosphorescent pigments, on antifreeze (for fire extinguishers not freezable at -25°) and on copper de-tinning.

The first doctoral student supervised by Demassieux, Jean Kranig, defended his thesis on the oxalic and carbonic complexes of trivalent cobalt in 1929.