Research on the role of non-governmental organizations (NGOs) in collective action predicts they will not interact with grassroots groups, citing partnerships with corporations and states, the apolitical delivery of social services and accountability towards donors as disconnecting professionalized actors from volunteer-based grassroots groups. Using interviews with core activists in the movement confronting Canadian resource extraction abroad, I depart from this approach by investigating the mechanisms, or threads, that bind organizations into coordinated action. I find that NGOs and grassroots groups coordinate as a result of: shared values and environmental justice frames, the allocation of resources, and engagement in complimentary forms of advocacy driven by a division of labour and a diversity of tactics. My research develops existing approaches to theorizing coordinated action and invites scholarship on NGOization to include the conceptual toolkit provided by social movement theories to better account for NGO–grassroots dynamics.