The inter-organizational lesson in the fight against terrorism has been clearly identified after 9/11, but not completely learned and applied. Horizontal cooperation and coordination structures have been established, yet due to many challenges they do not function optimally. This article reaches beyond the prevailing mantra concerning the need for inter-organizational cooperation in the fight against terrorism by providing a framework for understanding the complexity of network counterterrorism and the relevant challenges. It introduces four levels of complexity that must be comprehended in order to ensure an optimal and comprehensive strategic approach in this fight. Based on this, it argues that a successful counterterrorism strategy needs to provide capacities for multi-organizational, inter-organizational and network-horizontal cooperation, and the capacity to manage many related inter-organizational challenges. The conclusions also suggest that our societies are still not conceptually and practically ready to embrace a truly comprehensive network approach to a networked threat. The inter-organizational approach in the fight against terrorism is ultimately what organizations make of it.