Background/Aims: Recent research on mindsets has shifted from understanding its homogenous role on performance to understanding how classroom environments explain its heterogeneous effects (i.e., Mindsets x Context hypothesis). Does the macro context (e.g., societal level of student mindsets) also help explain its heterogeneous effects? And does this interaction effect also apply to understanding students' well-being? To address these questions, we examined whether and how the role of students' mindsets in performance (math, science, reading) and well-being (meaning in life, positive affect, life satisfaction) depends on the societal-mindset norms (i.e., Mindsets × Societal Norm effect). Sample/Methods: We analysed a global data set (n = 612,004 adolescents in 78 societies) using multilevel analysis. The societal norm of student mindsets was the average score derived from students within each society. Results: Growth mindsets positively and weakly predicted all performance outcomes (rs = 0.192, 0.210, 0.224), but the associations were significantly stronger in societies with growth-mindset norms. In contrast, the associations between growth mindsets and psychological well-being were very weak and inconsistent (rs = -0.066, 0.003, 0.008). Importantly, the association was negative in societies with fixed-mindset norms but positive in societies with growth-mindset norms. Conclusions: These findings challenge the idea that growth mindsets have ubiquitous positive effects in all societies. Growth mindsets might be ineffective or even detrimental in societies with fixed-mindset norms because such societal norms could suppress the potential of students with growth mindsets and undermines their well-being. Researchers should take societal norms into consideration in their efforts to understand and foster students' growth.