International organizations (IOs) were founded on the principles of fair representation and meritocracy, starting in the 1920s. From the League of Nations to post-Second World War IOs, all endorsed gender equality among their staff – however, none truly lived up to this promise. This thesis considers the progressive spread of gender equality through the lens of women’s career in the secretariats of IOs, with a focus on the League of Nations (LoN) and the United Nations (UN). It examines how international organizations framed gender equality, and how they selectively integrated women to their staff. This thesis confirms that IO secretariats cultivated a rhetoric a difference between men and women international civil servants, fostering systemic discrimination. A sociohistoric investigation of women’s secretariat careers then sheds light on the various strategies employed by women international civil servants to free themselves of these inequalities. This doctoral research thus connects the history of international bureaucracy with gender and women history. By exploring the gradual integration of topics such as the status of women and social welfare in the agendas of IOs, it rehabilitates women international civil servants in the intellectual history of international organizations.