This paper focuses on hegemony and its outcomes on international relations. A theoretical review of academic literature will be combined with an analysis of hegemony’s features and related policies in the contemporary international system. In the first part of the paper, I will look at the three schools of thought that offered the main theoretical frameworks to explain hegemony: long-cycle theory, world-system theory, and hegemonic stability theory. I will argue that these schools are not fully convincing in theorizing the relationship between system polarity and hegemony (defined as relation of power). In the second part of the paper, I will analyse the distinction that occurs between unipolarity i.e. the structural feature of the contemporary system – and US hegemony – i.e. the processual feature – and how the former influences the latter. In particular, I will focus on security issues, and suggest that unipolarity implies particularly difficult tasks to US hegemony, since it makes delegation in security provision very difficult, both in regional and domestic settings. In this respect, I will maintain that armed forces are important to carry out these difficult tasks, at the same time underlining the hegemonic weaknesses: The contemporary hegemon is relatively weak in this capability, and the political costs for use of this capability are high. Consequently, I will suggest the hegemonic power of the contemporary unipolar system needs multilateral and institutional support in order to manage world affairs also because of its superior power, and not despite of it.