Background: Neonatal sepsis remains a challenge for neonatal care providers. Aim: to measure red cell distribution width percent (RDW %) as a marker for neonatal sepsis severity and to correlate the determined severity with other indicators. Methods: This case control studywascarried out at neonatal intensive care unit at Assiut Al Azhar University Hospital from June to December 2015. Ethical Research Committee Approval and written consents were obtained from parents of the neonates 50 neonatal sepsis cases and 30 normal controls. Inclusion criteria: age from 1-28 days and had findings of sepsis either clinical or laboratory. Neonates were subjected to: History taking, clinical examination for manifestations of sepsis. Complete blood count- C- reactive protein, Blood culture and sensitivity and determination of RDW % were done to all neonates. Results: Mean RDW % was higher among cases than controls (18.35± 1.79 & 12.95± 2.23 respectively) (P < 0.001), meanwhile hemoglobin (HB) was lower in cases than controls P=0.094. WBCs were higher among cases compared to control (P =0.030). CRP was normal in all controls, and was higher in all cases. RDW % was higher in severe sepsis than mild (19.4 ± 1.8 % & 17.2± 0.58% respectively) (P < 0.0001), while HB and WBCs showed insignificant relation with severity of sepsis (p =0.299 and 0.129 respectively).  CRP showed significant relationship with severity of sepsis p<0.01. Conclusion: RDW % can serve as a marker and prognostic indicator in assessing severity evaluation and risk stratification of neonatal sepsis.