Background: Incident acute kidney injury (AKI) in critically ill patients with acute on chronic liver failure (ACLF) is associated with poor prognosis. The role of continuous renal replacement therapy (CRRT) is not well established for patients with ACLF and AKI. Materials and methods: We conducted a retrospective cohort study to examine clinical outcomes in 66 patients with ACLF and AKI requiring CRRT. Results: All-cause hospital mortality was 89.4%. Five (7.6%) patients were listed for liver transplantation, of whom 1 (1.5%) was eventually subjected to transplantation. Etiology of AKI included type 1 hepatorenal syndrome (HRS) with or without some degree of acute tubular necrosis (ATN) in 20 (30.3%) patients, and primarily ATN in 46 (69.7%) patients. When evaluated at the time of CRRT initiation, Child-Pugh-Turcotte (CPT) and Model for End-stage Liver Disease (MELD) (area under the receiver operating characteristics curve (AUROC) 0.67 for both) had fair performance for prediction of mortality, whereas Sequential Organ Failure Assessment (SOFA) and Chronic Liver Failure (CLIF)-SOFA performed better for the prediction of mortality (AUROC 0.87 for both). SOFA and CLIF-SOFA also performed well when determined at the time of ICU admission (AUROC 0.86 and 0.85, respectively). Etiology of liver disease or AKI did not influence prognosis. Conclusion: Critically ill patients with ACLF and AKI requiring CRRT have poor hospital survival, even with provision of extracorporeal support therapy. SOFA and CLIF-SOFA are good prognostic tools of mortality in this susceptible population.