This essay explores the mobilization of the migrant day laborers’ movement in search of lessons to inform a critical theory of cosmopolitan politics. In the course of the movement’s rise to national prominence in US immigrant politics, have day labor groups also developed forms of political consciousness and action that move beyond the narrow limits inscribed by the system of sovereign nation-states? How might considering the circumstances of day laborers influence the way theorists conceive of cosmopolitanism and, in turn, what aspects of the day labor movement stand out most sharply when viewed through the lens of cosmopolitan theory? The first part of this essay formulates a theory of cosmopolitan politics that reflects attentiveness to migrant workers’ everyday lives. According to this vision, cosmopolitanism should oppose neoliberalism, resist domestication by liberal legalism even as it pursues a politics of rights, deploy threads of connection across political terrains at multiple geographical levels, respond to subalternity with the dialogical commitments of popular education and through disruptions of the sensible order, and combat of the global deportation regime. In the second part of the article, we tell the story of the day labor movement’s origins and growth into both a national force in US politics and a participant in transnational alliances, following its beginnings as an assortment of dispersed struggles to improve local conditions for migrant workers. Throughout this history, the day labor movement gradually has come to demonstrate more and more of the features we argue should characterize a radical conception of cosmopolitan politics.