Background: A growing body of research has been examining neighborhood environment related to children's physical activity and obesity. However, there is still not enough evidence from Latin America. Objective: To investigate the association of neighborhood and family perceived environments, use of and distance to public open spaces with leisure-time physical activity (LTPA) and body mass index (BMI) in Argentinean school-aged children. Methods: School-based, cross-sectional study with 1777 children (9 to 11years) and their parents, in Cordoba city during 2011. Children were asked about LTPA and family perceived environment. Parents were asked about neighborhood perceived environment, children's use of public open spaces and distance. Weight and height were measured for BMI. We modeled children's LTPA and BMI z-score with structural equation models with latent variables for built, social and safety neighborhood environments. Results: Parents' perceived neighborhood environment was not related with children's LTPA and BMI. Children's perceived autonomy and family environment were positively associated with LTPA. Use of unstructured open spaces and, indirectly, the distance to these, was associated with LTPA among girls. Greater distance to parks reduced their use by children. Conclusion: Policies to increase children's LTPA should include access to better public open spaces, increasing options for activity. A family approach should be incorporated, reinforcing its role for healthy development.