Climate change can be viewed as human-induced change to climate and depletion of natural systems. It potentially the biggest global health threat of the 21st century. It is predicted to have wide-ranging impacts upon human mental health and well-being, through changes and challenges to people's environment, socioeconomic structures and physical security. Even the most conservative estimates of the health impacts are extremely alarming. Increasingly, the causes of poor human health and environmental damage are related. This implies that there are common solutions. For example, there are co-benefits to human health and biodiversity from mitigating and adapting to climate change (e.g. promoting active transport and reducing car use reduces CO2 emissions, benefits our environment and reduces morbidity and mortality associated with a sedentary lifestyle). This article outlines how climate change impacts upon mental health and well-being. It introduces ecological concepts, applies these to public health and outlines their implications in transforming the way that we prioritize and deliver public health in order to promote both environmental and human health. Evidence, from psychology and neuroscience, suggests that the perception of being disconnected from our inner selves, from each other and from our environment has contributed to poor mental and physical health. We argue that we must transform the way we understand mental health and well-being and integrate it into action against climate change. We describe a Public Health Framework for Developing Well-Being, based on the principles of ecological public health.