European cooperation on internal security is usually seen through the lens of highly salient normative debates, such as the appropriate balance between freedom and security. This paper provides an alternative and long-term perspective on this policy area. The first theoretical part condenses four alternative theoretical perspectives on European internal security governance that relate to the wider relationship between informal and formal governance mechanisms. The second part presents a matching empirical overview of more than 180 European governance networks on police and criminal cooperation, counterterrorism, border security, migration policy, cybersecurity and disaster prevention. Expertise-driven and policy field-specific dynamics appear significant to account for the breadth and variety of policy networks. In contrast, executive empowerment, venue-shopping or deliberate side-stepping of formal decision-making forums do not appear as dominant trends, although there are severe structural shortcomings with regard to the transparency and legal basis of the mapped policy networks.