Background: Platelets are heterogeneous in size, density, metabolic, functional, and biochemical properties. Mean platelet volume (MPV) is a measure of the average size of platelet in a blood sample. Objectives: The aim of the work was to study the relationship between MPV levels and the glomerular filtration rate (GFR) in pediatric patients with chronic kidney disease (CKD) and its role to be a marker for the disease progression. Patients and methods: Seventy-five children with chronic kidney disease subdivided into four subgroups according to GFR were included in this study. Seventy-five healthy subjects were enrolled as a control group. All subjects were subjected to detailed history taking, physical examination and Laboratory investigations. Pelvi- abdominal ultrasound used for diagnosis of chronic kidney disease, Tc-99m DTPA (diethylenetriaminepentaacetic acid) scan used for measurement of GFR. Results: MPV levels in the whole patient group were significantly higher than in controls (9.1±0.57fL versus 6.95±0.63fL). There were no significant differences between subgroups of patients with CKD as regard sex, age, weight, systolic, diastolic blood pressure, MPC and PDW while significant differences in disease duration and MPV levels were found among them. In patients with CKD, we have found a significant negative correlation between MPV and GFR. Also, we have found a significant negative correlation between MPV and Mean platelet count per thousand (MPC). Conclusion: It could be concluded that MPV value can be an easy, rapid, inexpensive, and simple marker for disease progression in pediatric patients with CKD.