Security Studies has portrayed states in the Global South as a threat to international security and overlooked insecurities experienced by people and social groups in the Global South. In security studies, security in the Global South has been explained in terms of incompleteness of states in the Global South. The dissertation questions how it is possible that security studies has accounted for security in the Global South in terms of a lack. The argument of dissertation is that the study of security in the Global South is related to the conception of modernity shaping security studies, which locates the Global South outside of world politics. This dissertation builds its argument in four steps. First, it identifies three dimensions of modernity, namely, time, ontology and sociality of world politics. These dimensions help to unpack conceptions of modernity in security studies, which vary across these three dimensions. Second, the dissertation unpacks conception of modernity shaping realist approaches to security and Third World security scholars’ analyses in order to examine their respective understandings of the relationship between the Global North and the Global South in security relations. Third, it asks how those, who are critical of these approaches, namely, critical and postcolonial approaches to security have understood the relationship. Fourth, the dissertation shows its argument by illustrating from studies on nuclear non-proliferation in the Global South.