Climate‐related security challenges are transnational in character, leading states to increasingly rely on intergovernmental organizations (IGOs)—such as the European Union and the North‐Atlantic Treaty Organization—for policy solutions. While climate security issues do not typically fit comfortably within the mandates of existing IGOs, recent decades have seen increasing efforts by IGOs to link climate change and security. This article reviews existing studies on IGOs’ responses to climate security challenges. It draws together research from several bodies of literature spanning political science, international relations, and environmental social science, identifying an emerging field of research revolving around IGOs and climate security. We observe significant advancement in this young field, with scholars extending and enriching our understanding of how and why IGOs address climate security challenges. Yet we still know little about the conditions under which IGOs respond to climate security challenges and when they do so effectively. This article discusses the main gaps in current work and makes some suggestions about how these gaps may be usefully addressed in future research. A better understanding of the conditions under which IGOs respond (effectively) to climate security challenges would contribute to broader debates on climate security, institutional change, and effectiveness in international relations and environmental social science, and may facilitate crafting effective global solutions to society’s most intractable climate security challenges.