Background: RDW predicts short-term outcome in critically ill AKI patients. RDW's long-term all-cause mortality prognostic value in children is unknown. Methods: one hundred PICU patients were studied. Clinical Pathology Department undertook laboratory tests. Scoring system used in this study are SOFA score which is a straightforward and objective measure to calculate organ dysfunction in six organ systems, APSIII score, RIFLE score and KDIGO classification. Results: RDW > 15.45 had 81.5% sensitivity and 60.3% specificity for predicting mortality. Statistically significant (p 0.001) Septic shock, high GCS, high SOFA score, high APS III, high initial blood creatinine, and high initial RDW are death risk factors. The higher initial serum creatinine wasn't an independent risk factor in multivariate regression analysis. RDW, KDIGO and RIFLE criteria had no correlation. Conclusion: Higher RDW was associated with increased mortality in critically ill AKI patients. Large prospective trials with longer follow-Up must corroborate our findings.