Popelin worked with Isabelle Gatti de Gamond in the development of women's education and, in 1888, became the first Belgian woman to receive a doctorate in law.

Along with her sister Louise, she taught in Brussels at an institution run by the leading feminist teacher Isabelle Gatti de Gamond from 1864 to 1875.

[9] Marie Popelin participated in two feminist conferences in Paris in 1889, and established the Belgian League for the Rights of Women (Ligue belge du droit des femmes) in 1892 with the assistance of Isala Van Diest and Léonie La Fontaine.

Popelin's efforts to create an independent feminist movement outside the political pillars, not linked to the Catholic, Liberal, or Socialist parties, were only a partial success.

[citation needed] These legislative reforms did not, however, include two of Popelin's most important demands: universal adult suffrage, and equal access to the liberal professions for women.

[10] In De Grootste Belg, a 2005 Flemish television poll to find the greatest Belgian of all time, Marie Popelin was ranked 42nd.