Co-management involves the shared administration of natural resources by two or more parties. This study examines the role of social capital in the process of developing co-management in three river corridors in Canada. Qualitative analysis reveals that social capital acts as a catalyst helping groups to progress through the stages of the co-management process. Forms of social capital (bridging and bonding) are identified that advance and/or inhibit the development of co-management. The article reaffirms the need to expand the institutional basis for natural resource management and provides empirical evidence that social capital plays a fundamental role in developing co-management. In conclusion, the article suggests that resource agencies need to recognize the value of social capital and the necessity for government representatives to be informed of and practiced in these skills, if they are to engage meaningfully with the civilian population.