To identify modifiable risk factors for obesity among low socioeconomic status (LSES) children. Cross-sectional data were obtained from 238 4-7-year-old children and 224 mothers from LSES preschools. Anthropometric measurements were obtained; mothers were interviewed about sociodemographic characteristics, health behaviors, perceptions and beliefs. The combined prevalence of overweight and obesity (OWOB) among children was 29.8% based on the new World Health Organization (WHO) growth standard. Prevalence of OWOB (body mass index ≥25) among mothers was 51.8%. Mean age, sleeping hours, gender distribution and poverty level were similar between normal and OWOB children. Over 82% of mothers underestimated their child's weight status. Of the 62 OWOB children, 74.2% were perceived by their mothers as having 'normal weight' (NW) and 8% were perceived as 'thin'. Mothers perceived 67 out of 158 NW children (42.4%) as 'thin' (P<0.001). Mediation analysis indicated that 10% of the effect of maternal underestimation on child's OWOB may be mediated through child's daily sedentary hours (P=0.06). In a multivariable logistic-regression analysis controlling for maternal obesity, knowledge regarding breakfast's importance and child's daily sedentary hours, maternal underestimation of the child's weight status (odds ratio=7.33; 95% confidence interval (CI):2.41-22.37; P<0.0001) and parental smoking (odds ratio=3.25; 95% CI: 1.26-8.40; P=0.015) were the only significant factors associated with OWOB in LSES children. Maternal perception of child's weight status and parental smoking are associated with childhood OWOB among LSES children. These parameters can help identify children at risk for obesity. Maternal perception may be amenable to intervention.