This article studies the relationship between nationalism and cosmopolitanism and suggests that they may be understood as mutually interrelated rather than opposed positions. Studying the modern versions of nationalism and cosmopolitanism from a sociological point of view requires also, philosophically, considering the moments of particularity and universalism in each of them. Whereas the particularism of nationalism depends on its capacity to provide our social and political identities with a sense of closing, the universalism of cosmopolitanism is focused on an inclusive notion of humanity. But cosmopolitanism also has a moment of particularism in terms of self-reflection on ‘our’ traditions and of doubt about ‘our’ deepest beliefs. Finally, the universalist moment of nationalism focuses on the principle of individual and collective self-determination, which cannot be normatively denied to others when accepted for one’s own group.