In this paper, we attempt to examine the sources of agency of target organizations when engaged in collective change processes organized by activists concerned with environmental issues and sustainable development in the eastern part of the Netherlands. In combining social movement and institutional entrepreneurship literature, we examine why and how target organizations engage in collective action, change their practices, and adopt new ones in the pursuit of solving a common issue with the help of activists. We found that motivations and intentions to contribute to collective action were instrumental in the beginning of their participation. However, as the project evolves, intentions changed through a reorientation of existing practices and positions in the collective change process of target organizations. This shift was caused by inaction and other setbacks where target organizations and activists were exposed. These changes in turn, set in new practice development and organizational forms necessary to continue collective change. With these findings, we contribute to an understanding of network mobilization by showing the emergent and dynamic character of collective change and especially indicate setbacks and inaction as both constraining and necessary condition for change.