(1) Background: Sustainability is a crucial priority and a critical part of the modern world. Promoting pro-social values to the younger generation is an issue addressed throughout this paper. The present study aims to answer the question of whether generosity, as a positive attitude towards others, and sustainability, as a positive attitude towards the environment, are related. (2) Methods: The current research includes a sample of 4333 adolescents, ages 14 and 15, who attend schools in Bihor County, Romania. (3) Results: The regression analysis indicates a significant correlation between sustainable values, operationalized through adolescent involvement in environmental organisations, and generosity. (4) Conclusions: Sustainable behaviour can be considered a form of giving that contributes to the collective good. Our research outlines a significant need for a new set of competencies provided through a newly designed curriculum and/or through focused training, in order to cultivate generosity across cultures, ecologies, and generations; at the same time, we also highlight the significant role that the joint efforts of the school-family-library trifecta in supporting this goal.