<p>Addressing environmental problems depends on individual willingness to make sacrifices in coordination with others, making them social dilemmas. Therefore, individuals who believe these problems are important may become unwilling if they expect others will not reciprocate. Therefore, social trust—a belief that people in general will behave pro-socially—is a predictor of environmental willingness. Environmental pessimism—the belief that the resolution of these problems is hopeless—is a negative predictor of willingness. We hypothesize that because of the negativity bias, pessimism will attenuate the effect of both trust and environmental concern in predicting environmental willingness. We test our hypotheses using multi-level models on the ISSP’s Environment IV dataset. We find that while social trust and environmental concern are positively associated with willingness, environmental pessimism diminishes the positive effects of trust and concern. We find both that individuals who have high social trust and environmental concern become less willing to make sacrifices for the environment than those who are less pessimistic. These results suggest that overcoming environmental pessimism is key to increasing support for addressing environmental problems.</p>