Urbanization leading to demographic shifts will have a profound effect on human health and bring challenges to urban sustainability. We reviewed the current research on this issue in China, Southeast Asia and East Asia. Urbanization in East Asian countries offers many opportunities for improvements in population health. However, it is also associated with health risks including air pollution, occupational hazards and traffic injury, and risks caused by dietary and social changes.Southeast Asia is a hotspot for emerging infectious diseases, and China is also a major contributor to the worldwide infectious disease burden because of its population size. Rural–urban migration combined with intercity or international travel could induce a wider spread of infectious disease between rural and urban areas, and even between cities worldwide. From the point of view of urban environmental planning, shaping cities towards a healthy future could assist in reaching sustainability targets. Japan provides many examples on how citizens can maintain health, such as universal health insurance coverage, less disparity between different socioeconomic groups, and strong community ties. Because of diverse geography and history, health status and health systems are often divergent across and within countries of Southeast Asia.