- The paper addresses tensions in organizing civil society activities in urban sustainability transitions. It argues that these activities need focus to be impactful while also demanding flexibility to remain adaptive. The latter can hardly be achieved by individual organizations alone but requires closer examination of the ecology of organizations in which civil society actors operate. This paper contributes to the literature on the governance of urban sustainability by systematically analyzing this organizational context and its long-term dynamics. Adopting a neo-institutional lens, the paper scrutinizes civil society activities with the ‘institutional work’ approach and sheds light on how the organizational context enables changes therein. The longitudinal case study of the Local Agenda 21 in Augsburg reveals, via a mixed-method approach, how civil society actors navigate tensions by altering their organizational context. Increasing its diversity and complexity in a bottom-up processThe paper addresses tensions in organizing civil society activities in urban sustainability transitions. It argues that these activities need focus to be impactful while also demanding flexibility to remain adaptive. The latter can hardly be achieved by individual organizations alone but requires closer examination of the ecology of organizations in which civil society actors operate. This paper contributes to the literature on the governance of urban sustainability by systematically analyzing this organizational context and its long-term dynamics. Adopting a neo-institutional lens, the paper scrutinizes civil society activities with the ‘institutional work’ approach and sheds light on how the organizational context enables changes therein. The longitudinal case study of the Local Agenda 21 in Augsburg reveals, via a mixed-method approach, how civil society actors navigate tensions by altering their organizational context. Increasing its diversity and complexity in a bottom-up process allowed them to engage in more transformative work.…