OBJECTIVES: This study aimed to examine the mediating effects of energy-balance related behaviors on the association of neighborhood socio-economic status (SES) and neighborhood residential area density (RAD) with body mass index (BMI). METHODS: In total, 6037 adults from four neighborhood types (high SES/high RAD, high SES/low RAD, low SES/high RAD, and low SES/low RAD) in five Mid-European urban regions completed an online survey asking about their energy-balance related behaviors (physical activity [PA], sedentary behavior, and dietary behavior), determinants of these behaviors and their body weight and height. MacKinnon's product-of-coefficients test was used to assess mediating effects. RESULTS: Transport-related PA, leisure-time PA and vegetable intake seemed to mediate the association between neighborhood type and BMI. Residents from low SES/low RAD neighborhoods reported less transport-related PA, less leisure-time PA and less vegetable intake than high SES/high RAD residents, and these behaviors (i.e. transport-related PA, leisure-time PA and vegetable intake) were related to having a higher BMI. CONCLUSION: The association between neighborhood type and BMI can be explained, at least in part, by energy-balance related behaviors.