Background: Ascites in cirrhosis has a poor prognosis, with mortality rates of around 40% at one year and 50% at two years. It is also associated with other complications, such as spontaneous bacterial peritonitis (SBP), which can lead to hepatorenal syndrome (HRS) in 30% of patients. Diagnostic paracentesis is the gold standard for diagnosing SBP. Serum biomarkers such as procalcitonin (PCT) have recently received a lot of attention for the early detection of SBP. Objective: To determine the usefulness of measuring serum procalcitonin levels in patients with liver cirrhosis and ascites for the diagnosis of spontaneous bacterial peritonitis. Patients and methods: A cross-sectional case-control study that was conducted on ninety (90) patients diagnosed with liver cirrhosis. They were divided into three groups: Group (A) included 30 cirrhotic patients with ascites diagnosed as spontaneous bacterial peritonitis, Group (B) included 30 cirrhotic patients with ascites but without spontaneous bacterial peritonitis,  and Group (C) included 30 cirrhotic patients without ascites as a control group. Results: Serum procalcitonin levels in SBP patients were significantly higher than in sterile ascites and cirrhotic patients without ascites with a P value of 0.001. It had a better cutoff value of 0.315 ng/ml, sensitivity of 87% and specificity of 97% than serum CRP that had a cutoff value of 16 mg/L, sensitivity of 76% and specificity of 90% in cirrhotic patients for predicting ascitic fluid infection. Conclusion: In cirrhotic patients, serum procalcitonin levels appear to provide a satisfactory diagnostic accuracy in the diagnosis of spontaneous bacterial peritonitis, with a suggested cut-off value of 0.315 ng/ml. Further studies are needed to determine the widespread use of serum PCT as a predictor of SBP clinically.