Child overweight and obesity represent a serious health problem worldwide. The Czech Republic now ranks the fourth most obese country in Europe and obesity and overweight is becoming more and more frequent in children and teenagers. This pilot study estimates the prevalence of obesity and overweight among Czech teenagers aged 14–15 years in terms of neighbourhood characteristics, and assesses the effects of neighbourhood environmental quality versus family or personal-level factors on teenage obesity and overweight. The results show that unsafe environments result in the risk of lesser physical activity of their inhabitants, but since the vast majority (92%) of the students felt safe in their neighbourhoods, mediation through safety of the neighbourhood is not at stake. Second, the housing estates demonstrate the most severe problems with both obesity and overweight and their built environments, but when perceptions of sporting facilities and similar opportunities for physical activity are factored in, they do not have low scores; therefore, mediation by physical activity is not a relevant response to the obesity problem. These findings imply that the most important obesogenic and obesoprotective factors are likely to be found within the family environment and personal life styles.