Consistently ranking among the most popular managerial approaches worldwide, strategic planning has become a centerpiece of public managers and policymakers’ toolbox to help answer fundamental questions about their organization, its aspirations and the capabilities needed to meet those aspirations. Strategic planning’s popularity can be explained by the assumption that it contributes to public service performance. Evidence to validate this belief was found in traditional public organizations. Critics, however, doubt whether strategic planning is also useful in complex, transnational public entities. So far, scholars have not yet looked into this. There is also a lack of research on how policymakers and public managers “do” strategic planning in such a way that it indeed generates benefits. My project tackles these two gaps in public administration research in the context of international public administrations (IPAs). Due to contemporary global challenges such as inequality and shifting economic and military relations, IPAs are becoming increasingly relevant. At the same time, we have little systematic understanding of how IPAs are managed and with which outcomes. By means of a systematic literature review and three qualitative process studies in the European Commission, the OECD’s Secretariat, and NATO’s International Staff, I aim to build a theory of strategic planning in IPAs that helps to understand how strategic planning can prove useful - or not - for such entities.