International, regional, and national organizations and policymakers are increasingly acknowledging the implications of climate on peace and security, but robust research approaches that embrace the complexity of this nexus are lacking. In this paper, we present the Integrated Climate Security Framework (ICSF), a mixed-methods framework to understand the mechanisms of climate–conflict linkages at different scales. The framework uses conventional and non-conventional methods and data to provide state-of-the-art policy-relevant evidence that addresses four main questions: how, where and for whom climate and conflict risks occur, and what can be done to mitigate this vicious circle. The framework provides a comprehensive assessment of the complex social-ecological dynamics, adopting systems approaches that rely on a combination of epistemological stances, thereby leveraging diverse qualitative, quantitative, locally relevant, and multifaceted data sources; and on a diversity of actors involved in the co-production of knowledge. Using a case study from Kenya, we show that the climate security nexus is highly complex and that there exists strong, theoretical, and statistical evidence that access to natural resources, livelihoods and food security are important pathways whereby climate can increase the risk of conflict, and that conflict undermines resilience objectives. We also find that communities in climate security hotspots are aware and highly knowledgeable about the risk that the climate crisis poses on existing drivers of conflict and yet, online issue mapping and policy coherence analysis indicate that policymakers have not been acknowledging the nexus appropriately. The policy-relevant evidence that is collected through the ICSF and collated in the CGIAR Climate Security Observatory aims to fill this gap and to help transform climate adaptation into an “instrument for peace”.