Background Spontaneous bacterial peritonitis (SBP) is a serious infection of ascitic fluid in cirrhotic patients. High mortality associated with the delay in diagnosis and treatment. There is a need for an accurate and a rapid method for SBP diagnosis. Objectives We aimed to evaluate ascitic fluid calprotectin as a diagnostic marker for SBP. Patients and methods Forty four cirrhotic patients were divided into two groups, non-SBP group: 22 patients with cirrhotic ascites without evidence of SBP and SBP group: 22 patients with cirrhotic ascites and SBP diagnosed by positive ascitic fluid bacterial culture and an increase in polymorphonuclear leukocytes (PMNLs) count in ascites (≥250 cells/mm3). Ascitic fluid calprotectin levels were measured using enzyme-linked immunosorbent assay. Results There was a significant increase of ascitic fluid calprotectin, total leukocytic count, PMNLs, lactate dehydrogenase, and total protein in SBP group when compared to non-SBP group. There were significant positive correlations between white blood cell, ascitic fluid total leukocytic count, PMNLs, total protein, and model for endstage liver disease score values and ascitic fluid calprotectin among SBP group. Ascitic fluid calprotectin with cutoff value 620 ng/ml, showed a sensitivity of 90.91% and a specificity of 95.45%, in diagnosis of SBP with positive predictive value 95.2% and negative predictive value 91.3%. Conclusion Ascitic fluid calprotectin may be valuable in rapid diagnosis of SBP. Keywords: ascites, calprotectin, spontaneous bacterial peritonitis