This chapter describes the relationship between climate change and security. Successive reports of the Intergovernmental Panel on Climate Change have provided growing evidence of the impacts of climate change. Climate change can affect human well-being in terms of access to water, food, energy, and land, as well as in terms of risks to human health. Thus, climate change is seen as a driver of other socio-ecological problems worldwide. Climate change is also seen as a risk and threat multiplier, as it can exacerbate existing challenges faced by States, including poor governance institutions and poverty. However, climate change policy could potentially be a ‘threat minimizer’ if mitigation and adaptation measures are integrated into the development paradigm. Against this background, the chapter addresses the following issue: What is the nature of the security debate raised by the climate change issue and how is this being addressed within scholarly, policy, and legal fora? It looks at the different ways in which security has been defined in the literature and its diverse implications for law and policy.