Background: Ascites is a main complication of cirrhosis that can be complicated by spontaneous bacterial peritonitis (SBP). A major predictor for mortality in this condition includes renal failure. Objective: The current study aimed to evaluate the value of serum kidney injury molecule-1 (KIM-1) in the early prediction of kidney injury in cases with SBP. Patients and Methods: A prospective cohort study was conducted on admitted patients with decompensated liver disease in Hepatology and Gastroenterology Unit, Specialized Medical Hospital, Mansoura University, Egypt. A total 160 patients were recruited; 120 patients with SBP (cases) and 40 patients without SBP (controls). Serum KIM-1 was measured for all patients. Additionally, serum creatinine (S.cr) was done every 48 hours during admission and every week after discharge. Results: A statistically significant lower AST, direct bilirubin, and Child-Pugh score was noticed in cases versus controls. Additionally, a significantly higher S.cr (on admission and at follow up), and KIM-1 in AKI vs. non-AKI was noted in cases vs. controls. Moreover, KIM-1, at a cutoff value of >88.6, had a high sensitivity and specificity (95.8% and 93.7%, respectively) in discriminating AKI from non-AKI patients. Conclusion: KIM-1 as a biomarker may allow evaluation of the functional condition, hepatorenal syndrome and acute tubular necrosis as a result potentially allowing early treatment decisions. In addition, this biomarker plays an essential role in early AKI diagnosis and overall prognostic assessment. This combination of biomarkers may be utilized to plan upcoming interventional researches in order to improve the outcomes of such cases.