Although many young people think climate change is an important societal issue, studies indicate that pessimism is quite common. Finding ways to instill hope could therefore be seen as vital. However, is hope positively related to engagement or is it only a sign of illusory optimism? The aim of the study was to explore if hope concerning climate change has a significant relation to pro-environmental behavior as well as an impact on behavior when controlling for already well-known predictors such as values, social influence, knowledge, and gender. Two questionnaire studies were performed, one with a group of Swedish teenagers (n = 723) and one with a group of Swedish young adults (n = 381). "Constructive" hope had a unique positive influence on pro-environmental behavior. Hope based on denial, however, was negatively correlated with pro-environmental behavior in the two samples and was a significant negative predictor in the teenage group. The conclusion is that hope is not only a pleasant feeling but could also work as a motivational force, if one controls for denial. Implications for education concerning sustainable development are discussed. (Contains 12 notes and 5 tables.)