The Librairie Honoré Champion of Paris and the Institut d’Estudis Catalans of Barcelona and its Library (Biblioteca de Catalunya) maintained business relationships for twenty-five years (1909-1936). In addition to serving as representative for France of the Institut’s publications, Champion was the major international supplier for the Biblioteca de Catalunya during its early years. This article examines the role of the Librairie Champion as supplier for the Biblioteca, particularly during the First World War under the direction of Marie Champion. The analysis of the surviving business correspondence, studied in its historical context, allows to sketch the figure of a woman who, amid the throes of war, succeeded in defending the family business while bequeathing the relationship between the Librairie and the Intistut a character intimately linked with her own personality.