Introduction: Despite treatment with antibiotic therapy, spontaneous bacterial peritonitis (SBP) accounts for approximately 20–40% mortality in hospitalized patients. The data is scarce regarding mortality predictors in SBP. Recently, multiple factors have been studied for effectiveness in prognosis prediction in SBP. Therefore, in this study, our main objective was to evaluate the mortality predictors in SBP. Materials and methods: This prospective observational study was conducted at the Department of Hepatogastroenterology, from January 2022 to June 2023. All the patients aged between 18 and 65 years having decompensated chronic liver disease and diagnosed with SBP were enrolled in the study. The excluded population comprised of those who were on hemodialysis, those having history of any solid organ malignancy or transplantation or patients suffering from infections such as those caused by human immunodeficiency virus (HIV) or infections other than SBP. These patients were followed during the hospital stay and after the discharge monthly for 3 months and then at 6 months to assess mortality. Results: A total of 142 cirrhotic patients having SBP were enrolled in the study. Among them, most of them were males [98 (69%)]. Viral hepatitis (65.4%) was the most common cause of cirrhosis in studied population. On univariate analysis, serum total leukocyte count (TLC), international normalized ratio (INR), ascitic TLC, ascitic neutrophils, ascitic lactate, ascitic LDH, CTP score, MELD-Na were significantly higher while serum albumin was significantly lower in the patients who died as compared to those who survived. However, on multivariate cox regression analysis, high serum TLC (p = 0.013), ascitic fluid lactate (p < 0.001) along with high CTP (p = 0.041) and MELD-Na score (p = 0.037) at presentation were the factors that were identified as an independent poor prognostic factors in SBP population. Conclusion: Cirrhotic patients with SBP are at increased risk of mortality. In our study we observed that high prognostic scores such as CTP and MELD-Na at presentation along with increased white blood cell counts and high ascitic fluid lactate levels at presentation are the potential and reliable predictors of mortality in SBP patients.