Below the surface of its central decision-making bodies, the European integration process has developed a dense web of transgovernmental ties that reach out to foreign regulators. Insofar as the latter gain formal participation rights in European Union (EU) regulatory bodies, this results into an external form of differentiated integration. Focusing on EU regulatory agencies, this contribution shows that external differentiation follows predominantly sector-specific functionalist dynamics that are only loosely coupled to Union overarching foreign policy prerogatives. In sum, these patterns highlight centrifugal dynamics of technocratic networking beyond the political confines of the EU's regional integration project.