European Union (EU) agencies like Frontex (the European Border and Coast Guard Agency), Europol (the European Union Agency for Law Enforcement Cooperation) and the EUAA (the European Agency for Asylum) developed a substantial policy-influencing, operational, regulatory, and implementation-influencing capacity. By developing standards and benchmarks, by training security staff all across the Union, as well as by overseeing that common rules and policies are implemented correctly, EU security agencies are more and more included in pinpointing political priorities, shaping security cultures, and developing foundational concepts (like those of risk and threat) upon which common interior policies are based. This Article explores the potential of EU agencies’ staff to socialise practitioners and decision-makers to certain security standards and practices and their perceptions of what public good they pursue (e.g., security vs. liberty). The Article argues that socialisation should be understood not simply as the transmission of EU norms to national officials, but as a mechanism through which administrative practices, professional expectations and understandings of appropriate conduct can become increasingly shared across jurisdictions. In the Area of Freedom, Security and Justice (AFSJ), where political sensitivity and national responsibility constrain the scope for uniform legislation, interaction between agency staff and national practitioners can therefore constitute an alternative pathway towards administrative convergence. At the same time, its effects depend on the incentives and political priorities of national practitioners.