(1) Climate change is highly inequitable, as the greatest risks are to the poorest populations, who have contributed least to greenhouse gas emissions. (2) We review the specific health vulnerabilities of urban populations in developing countries, and highlight the range of health effects of energy policies that are concentrated in urban areas. (3) The rapid economic development and urbanization of poorer countries mean that cities in developing countries will be both vulnerable to health hazards from climate change and, simultaneously, will also increasingly contribute to the problem. (4) Thus, climate change is not only an environmental issue; it is also an emerging threat to global public health.