["Child and Adolescent Mental Health, EarlyView. ", "\n\nBackground\nWhile numerous studies have explored factors contributing to poor mental health, few have examined the combined influence of multiple health and social factors and their cumulative effect. This study specifically aimed to analyze the cumulative effect of multiple health and social factors associated with poor mental well‐being in school‐aged adolescents (12–18 years old) in Central Catalonia during the 2021–2022 academic year.\n\n\nMethods\nCross‐sectional study using data from the 2021–2022 DESKcohort project, with a total sample of 9265 high‐school aged students in Central Catalonia (49.2% boys and 50.8% girls). To identify factors associated with poor mental well‐being (score < 44 on the Warwick‐Edinburgh Mental Well‐being Scale), Multilevel Poisson regression models with robust variance were estimated, obtaining prevalence ratios (PR) with their respective 95% confidence intervals (95% CI). The cumulative effect score was derived by summing the factors that were associated with poor mental well‐being.\n\n\nResults\nWe observe a gradient where the likelihood of experiencing poor mental well‐being increases statistically significantly with exposure to a greater number of multiple health and social factors. In boys, the prevalence ratio increases statistically significantly from PR = 1.59 (p < .040) to PR = 24.52 (p < .001) for 1 and 10 health and social factors combined, and in girls, increases statistically significantly from PR = 2.56 (p < .001) to PR = 16.23 (p < .001) for 1 and 11 health and social factors combined, respectively.\n\n\nConclusion\nThe findings of this study highlight the multifaceted nature of mental health and the co‐presence of multiple axes of inequality, where overall health, family and psychosocial factors, and health behaviors form a cumulative association with adolescents' poor mental well‐being.\n\n"]