Organizational overlap is a ubiquitous feature in regional governance. Most studies have focused on member states, demonstrating that overlap enables states differently. We still know little about whether and how overlapping organizations impact international bureaucracies and how this shapes the relationship between bureaucratic actors within organizations. We argue that overlap can empower international bureaucrats, but not equally. Those with autonomous resources from member states are the most attractive interlocuters for bureaucrats from other organizations and, hence, likely to become most empowered. Substantive expertise and formal competence are less consequential in this context. We unpack this argument by looking at a policy domain understood to be heavily guarded by member states, security and defence policy. Based on primary documents and interviews, we show that the European Union (EU)–North Atlantic Treaty Organization (NATO) overlap has enabled the European Commission to leverage its position within the EU to its advantage and further encroach on the EU's security and defence activities.