Increasing evidence suggests that contingent self-worth poses a significant risk to adolescents' psychological health, yet few intervention studies have explored ways to mitigate its negative effects. While correlational studies indicate that gratitude may counteract contingent self-worth, experimental research is necessary to establish causality. This study aimed to determine the impact of a 10-week gratitude intervention on reducing contingent self-worth and improving psychological health among 198 adolescents, with both immediate and three-month delayed post-test assessments. Participants were randomly assigned to one of four groups: (a) gratitude, (b) positive events, (c) hassles, and (d) business-as-usual. Results revealed that the gratitude group reported lower levels of academic and appearance contingent self-worth, alongside improvements in emotional instability, psychological flexibility, and symptoms of depression and anxiety, compared to the other groups in immediate post-tests. Although life satisfaction did not significantly differ among groups at the immediate post-test, the gratitude group exhibited higher life satisfaction and lower depression and anxiety levels at the delayed post-test. This study contributes to the literature by providing evidence for the causal relation between gratitude and reduced contingent self-worth with practical implications for interventions.