Networks are increasing in number and in importance across the security field as a means of providing inter-agency coordination. Based on a large qualitative study of networks in the field of national security in Australia, this article aims to advance our knowledge of the internal properties of public sector networks in the field of national security and the conditions shaping their performance. It puts forward a multi-level theoretical framework involving five interdependent levels of analysis-structural, cultural, policy, technological and relational-that aims to account for the internal properties of networks and examines each of these levels in relation to public sector networks in the field of national security. Using detailed interviews with senior members of security, law enforcement and intelligence agencies, the article aims to highlight the potential lessons this framework has for strategically organising and managing dynamic networks within and beyond the field of national security.