Together with the Netherlands’ Institute for Sport and Physical Activity (NISB) and fifteen National Sport Organizations (NSOs), representing over 3.2 million sport club members, this research project examines changes in membership and engagement in sport clubs. Combining a sociological, geographical and public administration perspective, we analyze to what extent people bond themselves to one another in sport clubs and are willing to engage themselves with their club. We zoom in on regional and social differences and variations with respect to each branch of sport. The study is based on a mixed methods design, including both quantitative and qualitative research and the application and assessment of interventions. The goal of the research project is to develop new insights into (changing) meanings of citizenship, membership and membership organizations in Dutch society in general and sport organizations in particular. In doing so, we intend to help Dutch sport organizations to successfully anticipate and respond to changing meanings that sport participants attach to club membership and engagement, and to contribute to wider scholarly and public debates on civil society and social cohesion.