Purpose: Prosociality may in part determine sustainability behavior. Prior research indicates that pro-environmental behavior correlates with prosocial attitudes, and separately, that prosociality correlates with social support in homes and communities. Therefore, prosociality may constitute a keystone variable linking human well-being with pro-environmental behavior. The purpose of the paper is to test this conjecture. Design/methodology/approach: Data from a multi-year student survey at the University of Maine on environmental behavior, prosociality and experienced social support are used. A two-stage least-squares regression is applied to explore the relationships between these variables, and sub-scale analysis of the pro-environmental responses is performed. Additionally, spatial statistics for the student population across the state are computed. Findings: The data corroborate previous findings and indicates that social support within a community may bolster the prosociality of its members, which in turn may increase pro-environmental behaviors and intentions. Research limitations/implications: Cross-sectional data do not permit the imputation of causality. Self-reported measures of behavior may also be biased. However, student prosociality surveys may provide an effective and low-cost sustainability metric for large populations. Social implications: The results of this study corroborate prior research to suggest that pro-environmental and prosocial behaviors may both be enhanced by bolstering social support efforts at the community level. Originality/value: It is suggested that prosociality could become a keystone sustainability indicator. The study's results extend the understanding of the connections between prosociality, social support and pro-environmental behavior. The results of this study suggest that efforts to simultaneously improve the well-being and environmental status might focus on building prosociality and social support systems at the community level.