The aim of this research was to explore a socially sustainable culture of participation in which all members of the community can be heard, make initiatives, express their opinions, and alter their practices. We conducted the study by analysing three separate sets of empirical research data in which participation was investigated in an early childhood education and care (ECEC) context and in club activities for children aged 4–12 and the elderly. The data include children’s perspectives regarding participation, ECEC practitioners’ perspectives on a culture of participation, and children’s and ECEC practitioners’ shared project-based practices. The results show that children and ECEC practitioners were willing to commit to new practices and construct a collective ‘we-narrative’. A we-narrative created a foundation for the conceptual model of a socially sustainable culture of participation, including the prerequisites of participation in adult practices, the goal of participation in children’s and adults’ shared activities, and a tool for strengthening participation. According to the results, a socially sustainable culture of participation is holistic and dynamic, and children can have an effect on daily activities, including basic care situations, as well as part of the educational activities.