Abstract Background and purpose: Overweight and obesity are the health problem in adolescents and the main purpose of this study was to evaluate this problem and some socio-demographicrelated factors among two ethnic groups in Iranian northern primary school children in 2010. Materials and Methods: This was a descriptive and cross-sectional study that performed on 4165 students (Turkman = 2852and Sisstani = 1313) from 112 schools in urban and rural area. The schools and students were chosen by cluster nad random sampling, respectively. Data collected by questioner which contain, questions on the social-economical condition of school children specially ethnicity, gender, location area, and economic status, for all samples through interview. Overweight and obesity classified based on the body mass index (BMI) cut off points of Centers for Disease Control values (in excess of the 85th and 95th percentiles, respectively). Spss.win16 software was used for analysis. Results: Linear regression analyzes revealed that weight, height, and BMI increase 2.70 kg, 4.62 cm and 0.42 kg in boys (P < 0.001) and 3.12 kg, 5.19 cm and 0.52 kg in girls (P < 0.001) every year, respectively. In total, overweight was common in 8.4% and obesity was common in 11.9% of students and they were statistically significant among two ethnic groups (P = 0.001) so, in Turkman group (14.1%) is more than in Sisstanish ethnic group (10.6%). As a result of logistic regression analyzes, the risk of overweight and obesity was 1.847 (1.546-2.208, confidence interval [CI] 95%) in Turkman group compared to Sisstanish ethnic group and it was 2.297 (1.911-2.761, CI 95%) in good economic group compared to poor economic group. Conclusion: Totally, one to seven of schoolchildren suffer from obesity and overweight and they were in Turkman ethnic group more than in Sisstanish ethnic groups. The important public health training about obesity for children especially in the urban area and high-income families emphasizes in this study.