A foremost question in resource and environmental management is how to build cooperative management (‘co-management’) arrangements reflecting principles of sustainability. To generate and test hypotheses about this question, I used participatory research methods in a five year case study of an aquatic management organization on the West coast of Vancouver Island. The organization was in a second phase of organizational development (Gray 1989) and was undertaking community self management, engaging in co-management over some management functions related to several species and issues, and negotiating for a robust co-management agreement over all management functions related to the area's aquatic ecosystem. Five main conclusions arose. First, building co-management involves static and dynamic elements. Some features remain constant white others evolve as participants go through stages of learning to work together. It is therefore essential to build commitment around stable elements and to think of co-management as an evolutionary process reflecting the natural history of a geographic area. Second, all organizations face persistent, classic organizational challenges when building co-management. These challenges are often overlooked, despite their impact on aligning concepts with the capacity to implement them. Organizations building co-management can have the incentive to transform these challenges into creative new approaches. Third, participants' motivations for engaging in co-management are essential to its success. A high degree of commitment born from a range of incentives and psychological motivations—including pride, identity and culture in an area—are important. Fourth, collaboration does not exist in a political vacuum. Tensions arise between those advocating collaboration and sustainability, and those either committed to the status quo or advocating change towards less sustainable principles and structures. This tension creates both challenges and opportunities. Finally, while building collaboration appears difficult and complex at one level, it is simple at another. Two principles, ‘hishukish ts'awalk’ (everything is interconnected) and ‘iisaak’ (respect with care), provide guidance to ‘leave agendas at the door’—opening and expanding participants' minds by letting go of mental habits and attachments. Uncovering space out of which new mutually-beneficial possibilities can arise is an essential element of successfully building collaboration.