How did intellectuals and politicians confirm or reinforce national categories, even when they ostensibly promoted visions of an international community? The article addresses this question through a case study of the League of Nations' mechanisms for intellectual cooperation. After a brief discussion of institutional aspects, namely the establishment of League-affiliated committees and institutes in the 1920s, the article focuses on the interplay of transnational and national practices. National actors – for instance intellectuals and organisations from Central and Eastern Europe – targeted the League bodies, evoking both cultural internationalism and national interests. Furthermore, nationhood was projected at international congresses – sometimes openly, sometimes in more subtle terms – with the pronouncements of delegates from Fascist Italy providing an interesting case in point. Finally, the article discusses how individuals sought to reconcile the multilayered nature of their activities; to this end, it considers several figures who were involved in the League’s efforts to foster a 'société des esprits'.