Background and study aim: The most common infection in decompensated hepatic patients with cirrhotic ascites  is spontaneous bacterial peritonitis (SBP), which occurs in the absence of an evident intra-abdominal source of infection. The aim of this work is to assess the value of calprotectin in ascitic fluid in diagnosis of spontaneous bacterial peritonitis in patients with liver cirrhosis. Patients and Methods: In this cross section study, 80 cirrhotic patients were divided into (group A) 40 patients with non SBP and (group B) 40 patients with SBP, who attended the Hepatology Department Benha University Hospital. All the patients were evaluated by thorough history, clinical examination, laboratory investigations, ultrasonongraphy, diagnostic paracentesis with PMNLs count and Calprotectin which was measured in 1 mL ascetic fluid by ELIZA. Results: Calprotectin was high in SBP group with a highly statistical significant difference in SBP group compared to non SBP group so it can serve as a sensitive and specific diagnostic test for detection of SBP in cirrhotic patients with ascites. The sensitivity of the test was 90% with specificity of 62.5%, PPV of 70.5% and NPV of 86.5% with the cut-off level were 2.98 ng /ml and the area under the curve was 0.88. Conclusion: Ascitic calprotectin reliably predicts PMN count >250/μL, which may prove useful in the diagnosis of SBP, especially with a readily available bedside testing device.