Background: The prevalence of primary school children obesity is rising at an alarming rate world wide children obesity have been observed in developed countries, however, its prevalence is increasing in developing countries as well. Aim :this study aimed To assess the obesity among primary school children through prevalence and associated factors. Subjects and method: Design : A descriptive cross-section research design the study. Setting : This study was carried out in five governmental primary schools in Port Said city region. subjects : A Cluster Sample was selected randomly it compromised of 697 students. Tool : Two tools were utilized to collect necessary data in this study. Tool one Interviewing questionnaire sheet was used to collect data about socio demographic character and life styles of children. Tool two body mass index. Results : The overall prevalence of overweight and obesity was 20.6%. revealed that the most independent significant predictors of overweight/obesity are, income enough 45.3% more than three quarter were eating during TV watch or computer use,33.3% were fast food ,50.7 % eating before bed and 68.8 % were no eating vegetables regularly, In addition, 41% no eating breakfast. Conclusion: This are a high significant relation between normal weight and over weight and obesity with eating habit and also eating out side the home and taking snakes. Recommendations: Educational efforts and reinforcement must be continuous to meet the needs of the parent and their children among primary schools