The aim of the two studies (N = 245 and N = 199) was to investigate the predictors of environmental guilt and analyze its mediating role between human-nature relationship and pro-environmental behavior intentions. In the first study, the connectedness to nature and social dominance orientation emerged as predictors of environmental guilt. In addition, guilt was an important mediator of the relationship between the connectedness and individual pro- environmental behavior. In the second study, guilt was predicted by gender, by locating the causes of the climate crisis in human activities rather than in the Earth's natural cycles, and by environmental nostalgia. In addition, guilt mediated the relationship between environmental nostalgia and willingness to engage in collective action and support systemic changes. Thus, environmental guilt seems to be an important factor in predicting a wide range of environmentally friendly activities: individual behavioral intentions, willingness to engage in collective actions, and support for systemic changes.