Community capacity for watershed management has emerged as an important topic for the conservation of water resources. While much of the literature on community capacity has focused primarily on theory construction, there have been few efforts to quantitatively assess community capacity variables and constructs, particularly for watershed management and conservation. This study seeks to identify predictors of community capacity for watershed conservation in southwestern Illinois. A subwatershed-scale survey of residents from four communities located within the Lower Kaskaskia River watershed of southwestern Illinois was administered to measure three specific capacity variables: community empowerment, shared vision and collective action. Principal component analysis revealed key dimensions of each variable. Specifically, collective action was characterized by items relating to collaborative governance and social networks, community empowerment was characterized by items relating to community competency and a sense of responsibility and shared vision was characterized by items relating to perceptions of environmental threats, issues with development, environmental sense of place and quality of life. From the emerging factors, composite measures were calculated to determine the extent to which each variable contributed to community capacity. A stepwise regression revealed that community empowerment explained most of the variability in the composite measure of community capacity for watershed conservation. This study contributes to the theoretical understanding of community capacity by quantifying the role of collective action, community empowerment and shared vision in community capacity, highlighting the need for multilevel interaction to address watershed issues.