Childhood hypertension is associated with early endothelial dysfunction and an increased risk of future cardiovascular disease. Endothelial extracellular vesicles (EEVs) have emerged as promising biomarkers of endothelial activation; however, their role in pediatric hypertension remains poorly understood. This observational case-control study aims to compare circulating EEV concentrations between normotensive children and children with newly diagnosed, untreated primary hypertension. The study will also investigate the associations between EEV levels, blood pressure, microvascular endothelial function assessed by laser Doppler flowmetry, and circulating biomarkers of endothelial activation. The findings may improve understanding of endothelial injury in pediatric hypertension and support the development of non-invasive biomarkers for early cardiovascular risk assessment.