Dual/multiple citizenship has become a wide-spread phenomenon in many parts of the world. Whereas during most of the 20th century it was seen as an evil which has to be avoided, today dual citizenship is it de jure accepted or de facto tolerated by most countries. The paper discusses the pros and cons of dual citizenship from the perspectives of six normative theories of democracy. For the more established theories – liberal, republican and communitarian democracy – we can draw on existing literature. From the perspectives of more recent and emerging theories of democracy – multicultural, deliberative and cosmopolitan/transnational democracy – the issue of dual citizenship has not been addressed yet. In consequence, I developed new arguments from core aspects of these theories of democracy for (and against) the normative desirability of dual citizenship. The most important innovation is the argument that in a world system which is characterized by the asymmetries of empires dual citizens can serve as representatives of peripheries with formal rights of political participation in central states. Overall, the analysis reveals – although in all theoretical perspectives we find arguments in favour and against dual citizenship – that the problematic aspects dominate only for communitarians. For all others, dual citizenship is a promising and important tool for strengthening democracy in a trans-nationalizing world.