The United Nations (UN) has been at the forefront of international policymaking on addressing the security implications of climate change, but other international organizations such as the EU, NATO and OSCE are also developing climate security policies. This is of particular interest to scholars focusing the evolution of the international human protection regime since these organizations are important actors in conflict prevention and peacebuilding. This paper seeks to answer the questions of how human security and state security is framed in climate security policies developed by the EU, NATO and OSCE, and what the role of groups of IO officials and diplomats is in shaping regional cooperation on climate security in Europe in a changing geopolitical context. The analysis draws on the concept of communities of practice, and it relies on a unique set of data derived from interviews conducted with diplomats and officials at the EU, NATO and OSCE as well as participant observation from relevant events organized by or in partnership with these organizations. A better understanding of how diplomats and officials work to promote regional cooperation on climate security is crucial to grasp the potential trade-offs between human security and state security in a rapidly changing climate where geopolitical tensions are on the rise.