This paper analyses Jürgen Habermas’s claim that democracy and human rights are co-original and its implications for his international theory. A central argument in his theory, the co-originality thesis suggests that human rights and democracy are not only both fundamental and mutually supportive, but also ‘equi-primordial’ and internally related. Reconstructing Habermas’s argument as it has developed over two decades, I argue that his account of constitutional democracy has difficulties accounting for the enmeshment of constitutional and international human rights, while his three-tiered model of global governance, in the absence of democratic legitimation, amounts to a downgrade of the currently institutionalized practice of international human rights. Instead, I suggest that shifting the focus from ideal global institutions to actual processes of domestic contestation, through which groups appropriate and apply international legal norms in order to claim their rights, provides a plausible account of the practice of international human rights consistent with the co-originality thesis.