Background and study aim: Some of patients with decompensated cirrhosis will exhibit newly developed acute liver failure. This condition is called acute-on-chronic liver failure (ACLF). Acute kidney injury (AKI) is common with ACLF. Kidney injury Molecule-1 (KIM-1) is an ideal biomarker of AKI. The aim of this study was to evaluate role of KIM-1 in prediction of AKI in ACLF patients. Patients and Methods: Eighty four patients were included in this study. They were selected from hospitalized patients with acute decompensated cirrhosis. They were allocated into two groups; group I: patients with no acute-on-chronic liver failure (ACLF), group II: patients with ACLF. Results: KIM-1 was significantly higher in the ACLF (group II). KLM-1 median was 2.4 in group I vs 7.35 in group II with p value <0.001. We found that at cut off value of ≥0.5 KLM-1 can predict the presence of AKI with sensitivity of 85.7%, specificity 88.1%, positive predictive value 87.8%, negative predictive value 86%, accuracy 86.9% and AUC= 0.867 p <0.001. Conclusion: KLM-1 rises significantly in patients with ACLF. KLM-1 can be reliable in prediction of the presence of acute kidney injury in decompensated cirrhosis.