Current literature tends to see cosmopolitan identity formation as an individual endeavour of developing a stance of openness, and transcending discourses of national and other cultural identities. This article challenges the essentialism inherent in this model by proposing a different framing of cosmopolitan identity formation that shifts the focus to how people collectively mobilize cosmopolitanism as a resource for cultural identity construction. The article is based on an anthropological study of transnational professionals who are part of a diverse expatriate community in Amsterdam. The analysis shows how these professionals draw on cosmopolitanism to define themselves as ‘non-nationals’. This involves downplaying national affiliations and cultural differences while also marking national identity categories and ‘cultural features’ to maintain the difference they collectively embrace. This, however, does not imply openness to all otherness. Boundary drawing to demarcate the cosmopolitan ‘us’ in relation to national (mono)culture is equally important. The article argues that cosmopolitan identities are socially accomplished as particular modes of collective belonging that are part of – not beyond – a global discursive sphere of identity politics.