Cross-sectional associations between sociocultural factors and objectively-measured physical activity in a sample of 397 children (aged 9) and 213 adolescents (aged 15) were investigated. Associations with children's physical activity were found for mothers' physical activity (Beta = 80, p < .01), parental participation (Beta = 67, p = .01), mother's age (Beta=-8, p < .01) and, in girls, fathers' physical activity (Beta=73, p = .045; R2 for final model: 10.6%). No sociocultural factors were significantly associated with adolescents' physical activity. Parental factors might be important targets for interventions to increase children's physical activity but other factors may have greater influence. For adolescents' physical activity, factors from other domains may be more important to target.