Abstract Background: Spontaneous Bacterial Peritonitis (SBP) is a fatal complication of liver cirrhosis. Early diagnosis and appropriate management is crucial as regard patients' survival. Aim of Study: To assess the value of serum Pro-calcitonin in diagnosis of Spontaneous Bacterial Peritonitis (SBP) and predicting its response to treatment. Patients and Methods: Forty eight patients with ascites and suspicion of peritoneal fluid infection were enrolled. Diagnosis of SBP was confirmed by ascitic fluid analysis in 24 patients. Serum Procalcitonin was measured at time of admission for all enrolled patients and after 5 days of antibiotic treatment for those with SBP. Results: At a cut-off of value of 0.55ng/mL, procalcitonin had the best sensitivity (100%), specificity (83.3%) and (99.9%) accuracy in predicting SBP diagnosis. After 5 days of antibiotic treatment, thirteen patients (54.2%) responded to treatment. Procalcitonin had a (100%) sensitivity, (87.5%) specificity and (100%) accuracy at a cut-off value of 0.45ng/mL in predicting response to antibiotic treatment. Conclusion: Procalcitonin may be a valuable non-invasive marker for diagnosis and guiding antibiotic therapy for patients with SBP.