This study investigates the links between parents' perceptions of their social and built residential environment and obesity among Portuguese school boys and girls. A total of 1885 children, 952 girls and 933 boys, aged 3.0-10.0 years, were observed. The children's weight and height were measured, and their parents filled out the "Environmental Module" questionnaire of the International Physical Activity Prevalence Study. Age and sex-speci`fic BMI cut-off points were used to define being overweight/obese. Environmental characteristics were combined into 2 composite neighborhood indices that were used as predictors in logistic regression models. Girls living in neighborhoods perceived as having poorly built environmental conditions had increased odds of being obese (OR=1.47; p<0.005), and girls living in neighborhoods perceived as being unsafe and dangerous had also increased odds of being obese (OR=1.339; p<0.005). These relationships were not evident for boys. Improvements in the neighborhood environment could be a strategy for tackling the growing epidemic of childhood obesity and can simultaneously contribute to reduce health inequities across population subgroups.