Abstract Background Healthy lifestyles may contribute to better mental health, which is particularly important in adolescence, an age at which half of all mental health problems first occur. This association may be even more relevant in adolescents of low family affluence, who show more mental health problems, as well as more unhealthy lifestyles. This study investigated healthy lifestyle behaviors, namely sufficient sleep and physical activity, daily breakfast intake, low levels of alcohol use or smoking, in relation to mental health and symptoms of mental health problems (feelings of depression, anxiety, stress and self-esteem) among adolescents from different family affluence. Furthermore, the moderating role of family affluence was examined in those relations. Methods Adolescents aged 12-18y were recruited via a random sample of schools in Flanders, Belgium. A total of 1037 adolescents participated (mean age = 15.2, 49.8% female). Independent samples t-tests, Mann Whitney U-tests and χ2-tests determined the differences in healthy lifestyle behaviors and mental health indicators between adolescents of low-medium and high family affluence. Regression analyses assessed the association between healthy lifestyles and mental health outcomes and the moderating role of family affluence. Results All healthy lifestyle behaviors were associated with at least one mental health outcome, with the exception of alcohol consumption. Adolescents from low-medium family affluence had lower levels of physical activity, less often took breakfast, had lower levels of alcohol consumption and reported lower self-esteem than adolescents from high family affluence. The results showed no moderating effect of family affluence for the association between healthy lifestyle and mental health. Conclusion These findings support the value of integrating healthy lifestyle behaviors in interventions for mental health promotion, for both youth of low-medium and high family affluence.