The beginning of the 21st century, marked by increasing international tensions, urged developed states to devise new, complex approaches to addressing the challenges of fragile states. The conceptual framework for relevant programmes and strategies was provided by the concept of ‘security–development nexus’, which rapidly became widely adopted in official documents of donor countries. Implementation of those programmes and strategies predominantly involves promoting and strengthening inter-agency collaboration. In the Federal Republic of Germany the priority is given to enhancing cooperation between the defense community and civilian aid agencies and funds, providing assistance to fragile and post-conflict states. This paper examines the establishment, current state and prospects for such collaboration in the FRG. The first section reviews the principal sources which depict the approaches of the key German agencies to the challenges of inter-ministerial cooperation. The second section examines official documents that characterize the context and origins of the idea of strengthening inter-ministerial interaction as a necessary condition for engagement in fragile states and the first steps in this direction. The authors emphasize that from the very beginning this process was marked by a growing gap between official rhetoric and practical implementation of programmes based on the ‘security-development’ paradigm. Intensification of inter-agency cooperation came with the NATO 2006 Riga summit, in particular, with the approval of the concept of ‘comprehensive approach’, which was introduced with minor amendments into official discourse of the German ministries and agencies in the form of ‘net security’ or ‘Vernetzte Sicherheit’. The third section examines challenges and prospects for implementation of the latter concept in promoting cooperation between German military and civilian institutions. The authors come to the conclusion that in the FRG, despite some progress, inter-ministerial cooperation in providing assistance to fragile states has been difficult because of a mutual mistrust between military and civilian experts, and its future depends on the political will of the German government.