The development of age-friendly cities and communities has become an important area of work in the fields of public health, ageing and public policy. This development reflects several larger trends including the complexity of demographic change and the recognition of the role of the environment in healthy ageing. In 2017, there were an estimated 962 million people aged 60 years or older worldwide, that is, around 13% of the global population. This part of the population is growing at an annual rate of about 3% and further growth is almost inevitable. An increasing part of this population lives in cities, where the combination of urbanization and ageing leads to new public health challenges, such as a higher risk of mental disorders, resulting in impairments in the ability to function socially. However, while cities pose major challenges for older citizens, they also offer opportunities for the implementation of policies and interventions that promote public health. In 2006, the World Health Organization (WHO) initiated a programme specifically targeting the health of urban residents aged 60 years and older, linking the challenges of urbanization and ageing. This collaborative programme aimed to identify which features of the built and social urban environment are essential in creating sustainable and supportive environments for older residents, and culminated in the publication of the Age-friendly city guide in 2006. An age-friendly city was defined as a place that encourages active ageing by optimizing opportunities for health, participation and security to enhance quality of life as people age. Starting with 33 cities, WHO built on the guide by launching the Global Network for Age-friendly Cities and Communities in 2010, currently consisting of more than 500 cities where more than 155 million people live. The network has reached several of the guide’s objectives, such as generating greater recognition of the implications of population ageing on urban planning and involving stakeholders at multiple governmental levels. At the same time, some of the network’s limitations must be considered, as age-friendly initiatives often compete with wider objectives associated with economic growth and development. Furthermore, exchange between the age-friendly city movement and related debates in urban geography, sociology and other social sciences remains limited. This gap is most notable around research on structural urban changes, such as the rise of global cities, widening socioeconomic inequalities, and the impact of rural migration. With increasing population ageing and urbanization, the development of age-friendly environments is a topic that demands the attention of both researchers and policy-makers. Two approaches hold the potential to move age-friendly city research forward: integration of determinants of ageing at multiple levels and the dynamics of urban environments.