Background: Acute kidney injury is an important risk factor for morbidity and mortality during critical illness notably in very old patients admitted to intensive care units. This study was performed to identify prognosticators for these patients.Methods: This single-center retrospective study is based on a patient registry of a medical intensive care unit. Hospital records of patients aged 80 years or older who were admitted between 2005 and 2015 were examined. Patients who developed AKI according to KDIGO guidelines within 4 days after admission were included in this study.Results: Ninety six (96) patients with AKI and 81 age-and gender-matched controls without AKI were included in this study. Mean APACHE II score was 30 with an ICU mortality of 27% in very old patients with AKI. The odds ratio to die in hospital for these patients was 5.02 in comparison to controls (49 vs 16%). APACHE II score and fluid balance in the first 2 days of ICU admission were the strongest predictors of ICU mortality with an AUROC of 0.76. Of the 47 patients with AKI who survived hospital admission, 30 were discharged home. Conclusion:Mortality is increased in very old ICU patients with AKI. Among survivors, two-thirds returned home.