Background: Increased carotid intima-media thickness and ventricular hypertrophy are two examples of the target organ damage that can occur in children with hypertension, which also raises the chance of developing cardiovascular disease later in life. Objective: To determine prevalence of high blood pressure (HTN) among primary school children in the City of Dyarb Negm, Sharqia Governorate and determining the causes of high blood pressure in kids. Subjects and methods: This is a cross-sectional study that we carried out from September 2018 to March 2019. The sample was calculated to be (817) students. All children were subjected to questionnaire filled by parents asking about: Personal data and family medical history. Measurements taken for each student were weight, height, and blood pressure. Results: HTN were (37 cases) 4.5% (3.2% stage 1 and 1.3% stage 2) and pre HTN (76 cases) 9.2%, and normal were 86.4%. Pre hypertension and HTN cases were significantly associated with high social class and HTN was significantly associated with low social class. HTN and Pre HTN cases were significantly associated with obesity and overweight. Diabetes mellitus (DM), HTN and obesity positive family history were significantly associated with HTN then Pre HTN. Conclusion: HTN among studied group was found in 37 cases (4.5%; 3.2% 1^st grade and 1.3% 2^nd grade). This study provides important evidence of the association between obesity, based on BMI and high blood pressure. HTN was significantly associated with high salt intake, higher number of meal and high caloric diet. Family history of HTN and obesity were significantly associated with HTN then Pre HTN.