<p>This systematic literature review investigates the complex relationship between religiosity and adolescents’ mental health. While previous research has often highlighted the benefits of religiosity for wellbeing, this review synthesises findings from ten studies across multiple countries and religious contexts to examine how religiosity relates to adolescents’ mental health, conceptualised broadly as encompassing emotional, psychological and social wellbeing. Seven databases were searched using explicit inclusion and exclusion criteria, and studies were critically appraised using Gough’s Weight of Evidence framework. Findings reveal that religiosity can enhance adolescents’ mental health by promoting purpose in life, happiness, life satisfaction, self-esteem, and positive affect, and by buffering against anxiety, depressive symptoms, and stress from discrimination. A limited number of studies showed that&#xa0;religiosity can also have neutral or negative effects, particularly when adolescents display extrinsically motivated or passive religious engagement, or hold rigid or negative attitudes toward religion. The review highlights gaps in the literature, including limited exploration of psychological and social wellbeing, the mechanisms through which religiosity influences mental health, and cross-cultural variations. Implications for schools, psychologists, and adolescent mental health interventions are discussed, alongside recommendations for future longitudinal, qualitative, and culturally diverse research to more comprehensively understand how adolescents’ religiosity can both support and challenge mental health.</p>