The European Union’s emergence as a supranational actor in political-security affairs represents a rare development that challenges realism, the dominant state-centric theory in international relations. Given that realism traditionally denies any significant role for non-state actors in the realm of security, a critical question arises: how does realism, along with its various strands, interpret and evaluate the EU’s agency in political and security matters? Initially, realism paid little attention to the EU’s security developments, viewing it merely as a non-state entity. However, with the formation of the Common Foreign and Security Policy (CFSP), the Common Security and Defence Policy (CSDP), and the establishment of the European Rapid Reaction Force, realists were compelled to engage with the EU’s evolving role. Although all realist branches remain skeptical of EU political-security integration, due to their emphasis on the primacy of states, national interest, and sovereignty, defensive neorealists, who acknowledge the role of institutions in fostering security cooperation among states, tend to adopt a more optimistic perspective. They offer a relatively favorable view of the EU’s gradual political and security convergence.