This study is to examine the effect of religion on pro-environmental behaviors in a Muslim developing country, using a religiosity-based subjective norm structure rather than important others in the theory of planned behavior. Data collected from 460 families revealed important insights into the religiosity-based subjective norm, planned behavior theory, and three pro-environmental behaviors. The findings implied that an important minority with a strong foundation or belief may have been more influential than many important others in the formation of a subjective norm. The research model worked seamlessly for pro-environmental behaviors at home and in purchasing. However, for pro-environmental transportation behavior, all predictors failed, including intention. Religiosity-based subjective norm had significant power in both influencing other planned-behavior structures and indirectly influencing pro-environmental behavior at home and in purchasing. These results could be used by governments, policymakers, and researchers to design and implement effective environmental management systems.