To provide the most recent estimate of childhood obesity and determine the trend in childhood obesity in Riyadh city over the past two decades, by comparing our results with previous studies that published data comparable to our study in terms of geography, sample age (6-16 years), and use of World Health Organization (WHO) cut-offs to define obesity.A cross-sectional study was conducted in 2015 among school children in Riyadh city. A sample of 7930 children (67% girls) aged 6-16 years were randomly selected. Body mass index for age and gender above +1 and below +2 standard deviation scores (SDS) defined overweight (SDS, z-scores) and >+2 SD scores defined obesity.The overall prevalence of overweight and obesity was 13.4% (14.2% for girls and 12% for boys; P= 0.02) and 18.2% (18% for girls and 18.4% for boys; P = 0.73), respectively. When compared with the WHO-based national prevalence rate of obesity reported in 2004 (≈9.3%), the obesity rate has doubled over a 10-year period. There was a significantly higher prevalence of obesity in adolescents (>11 years) than in children (20.2% vs 15.7%; P < 0.01). Overweight and obesity increased significantly with higher levels of socioeconomic status. Obese children were at 1.5 and 2 times risk of developing gas bloating and vomiting than non-obese children.The prevalence of overweight and obesity has risen alarmingly among Saudi children and adolescents over the past decade and should make a strong case to initiate and monitor effective implementation of obesity prevention measures.