The present study estimated the prevalence of childhood obesity and identified risk factors in 10-13 year old children. A cross-sectional study was conducted, including 200 children and their parents, in seven randomly-selected primary schools across Patras, Greece. Height, weight, and waist circumference were measured, and self-reported information was collected via face-to-face interviews. Body mass index was calculated for the children and their parents. The effect of risk factors on overweight and obesity was analyzed using regression analysis. The prevalence of overweight and obesity was 32% and 10.5%, respectively. The odds of being overweight/obese increased in children whose parents had a lower educational level and/or higher body mass index. Fewer daily meals and more time spent in front of the television and/or on the computer were significantly associated with obesity in 10-13 year old children. The prevalence of excess weight in primary school children in Patras is of concern, especially for boys. Children's nutritional habits, leisure activities, and parental characteristics influence their somatometric characteristics. These findings highlight the need for future weight loss interventions targeted at this population.