Abstract Background Vitamin D has pleotropic effect including the immune function, it increases innate immunity and modifies lymphocyte activation. The risk for bacterial infections is increased in cirrhotic patients due to low levels of vitamin D, so its deficiency may be linked with the prevalence of SBP in cirrhotic patients Aim of the work To assess the 25-OH vitamin D serum level in cirrhotic patients and it’s relation to spontaneous bacterial peritonitis. Patient & Methods The current study included 90 patients divided into three groups; group one; patients with compensated liver cirrhosis, group two; patients with decompensated liver cirrhosis without SBP and group three; patients who had decompensated cirrhosis with SBP. The following laboratory work up was done: Serum 25-OH vitamin D level, liver functions test, kidney functions test, complete blood count, and ascitic neutrophil count. Results We report a highly significant difference between the studied groups as regards 25-OH vitamin D level, being lowest in group three. A negative correlation between markers of severe cirrhosis and vitamin D concentrations was found in our cirrhotic patients. Conclusion Vitamin D deficiency is associated with increased incidence of infections in cirrhotic patients including spontaneous bacterial peritonitis, suggesting that Vitamin D supplementation may be useful in these patients.