This is a descriptive cross-sectional study that was carried out at Khartoum State during the school year 20112/2012 to estimate the prevalence of obesity among school children aged 6-15 years and to investigate the relationship between BMI (Body Mass Index) and socioeconomic status and life style factors. Two hundred and fifty pupils participated in this study. The researcher took the anthropometric measurement inside the class room and gave the questionnaire the students to be answered by one of child’s parents. The data was analyzed using the Statistical Package for the Social Sciences (SPSS Version 13.0). In this study, prevalence of obesity was found to be (48%) of them 18% males and 30% females. Income of the family, number of high caloric carbonated beverages/week, way of transportation to school, length of daily playing outside the home, and time spent in watching TV and video games were significantly correlated with student’s BMI. While parent’s BMI was not having significant correlation with student’s BMI. This study is considered as the first study in its field regarding this age category in Khartoum State, and it is promoting future researches in obesity and its determinant. Key words: Obesity in relation to risk factors and socioeconomic conditions among school-age children