This working paper is part of a collaborative project, ‘Business and International Order’, between ECOINT and Pierre Eichenberger and Thomas David from the University of Lausanne. Women’s contributions to business internationalism remain an understudied subject. This paper helps to address that gap by enquiring about the women that worked for the International Chamber of Commerce (ICC) since its foundation in 1920. We argue that accounting for mid-level thinkers demonstrates the crucial, hidden importance of women to ICC policy work, especially after 1945. The ICC was the first international business organisation to exist permanently and emulated the League of Nations (LON) by creating a professional secretariat. The first and second parts of the paper contextualise the employment of women in ICC headquarters against the example of the LON. We show that during the interwar years, women were mostly relegated to secretarial tasks. An epochal shift took place after World War Two, as covered in the third section, when women started being employed as economic and legal officers. They also participated in the all-important ICC congresses as external experts or businesswomen in their own right. UN efforts to regulate international trade immediately attracted the ICC’s attention. Through the biographies of four ICC officers (Marie-Constance Psimènos de Metz-Noblat; Edith Sansom; Roberta Lusardi; and Janette Buraas), we demonstrate how women represented the ICC in the United Nations’ forums. We conclude by reflecting on how accounting for women as mid-level thinkers changes historical understandings of the ICC and opens new paths of research.