BackgroundThe objective of the study was to analyze the associations of family aspects, physical fitness, and physical activity with mental-health indicators in a sample of adolescents from Colombia.MethodsA cross-sectional study carried out in a sample of 988 adolescents (11-17 years-old) from public schools in Montería. Mental-health indicators were evaluated: Stress, depression, anxiety, happiness, health-related quality of life (HRQL), and subjective wellness. Family aspects included family affluence, functionality, and structure. These variables, along with physical activity and screen time, were measured with questionnaires. A fitness score was established by assessing the components of fitness: Flexibility, cardiorespiratory fitness, grip strength, and lower-limb strength. Associations were analyzed by multivariate linear regression models.ResultsNuclear family structure was associated with lower stress level (− 1.08, CI: − 1.98 - -0.18), and family functionality was associated with all the studied mental-health indicators (Stress: -0.11, CI: − 0.17 - -0.06; depression: -0.20, CI: − 0.25 - -0.16; trait anxiety: -0.13, CI: − 0.18 - -0.09; state anxiety: -0.12, CI: − 0.17 - -0.08; happiness: 0.09, CI: 0.07 - 0.1; HRQL: 1.13, CI: 0.99 - 1.27; subjective wellness: 1.67, CI: 1.39 - 1.95). Physical activity was associated (β, 95% Confidence Interval (CI)) with depression (− 0.27, − 0.57 - -0.02), trait anxiety (− 0.39, CI: − 0.65 - -0.13), state anxiety (− 0.30, CI: − 0.53 - -0.07), happiness (0.14, CI: 0.06 - 0.22), HRQL (3.63, CI: 2.86 – 4.43), and subjective wellness (5.29, CI: 3.75 – 6.83). Physical fitness was associated with stress (− 0.80, CI: − 1.17 - -0.43), state anxiety (− 0.45, CI: − 0.73 - -0.17), and HRQL (1.75, CI: 0.82 - 2.69); screen time was only associated with stress (0.06, CI: 0.02 - 0.11).ConclusionsFamily aspects were associated with mental health indicators, especially family functionality which was associated all mental-health indicators. Similarly, fitness, physical activity, and screen time were associated with the studied indicators of mental health. Particularly, physical activity was associated with all the mental-health indicators, except stress, which was only associated with screen time. Physical fitness was associated with stress, anxiety, and HRQL. Future studies could explore the causal relationships of fitness, physical activity and screen time with mental health in adolescents.