Research has shown that an individual's cognitive flexibility predicts their pro-environmental behavior (PEB). However, the cross-country variations in this relationship are not yet clear. Using an international dataset from PISA 2018, this study examined the relationship between cognitive flexibility and PEB and the role of cultural factors in the above relationship among 368,045 adolescents from 60 societies. The results showed that adolescents' cognitive flexibility positively and significantly predicted their PEB. However, the observed cognitive flexibility-PEB relationship does not operate in a sociocultural vacuum. The study identified individualism and uncertainty avoidance weakened adolescents' cognitive flexibility-PEB association; whereas cultural tightness strengthened this association. Therefore, the findings of this study extend our understanding by illuminating not just the role of individual cognitive processes, such as cognitive flexibility, in shaping adolescents' PEB, but also emphasizing the critical interplay between individual cognitive capabilities and the overarching sociocultural context. The nuanced interdependence between these factors provides rich ground for future research in the realm of cognitive and environmental psychology.