Acute kidney injury (AKI) is a risk factor for increased mortality in critically ill patients. To assess the incidence, risk factors and outcome of patients who develop AKI in the intensive care units (ICUs), we retrospectively studied 235 patients admitted to the ICU of Shahid Mohamadi Hospital, Hormozgan, Iran, and compared those who developed AKI and those who did not. There were 31.1% of patients who developed AKI during ICU admission. There was a significant difference in the mean age, serum sodium (Na), potassium (K), urea, blood urea nitrogen (BUN) and creatinine (Cr) levels and also platelets, on admission, between patients with and without AKI. Acute physiology and chronic health evaluation (APACHE) II score on admission was significantly higher in AKI patients and Glasgow coma scale (GCS) was significantly lower. The mortality of AKI patients (72.6%) was significantly higher than non-AKI patients (25.91%). The number of underlying diseases and GCS and APACHE II score on admission were significantly different between the expired and survived patients. We conclude that age, first serum K level and APACHE II score on admission time were powerful independent predictors of developing AKI in ICU patients. The GCS on admission and the presence of two or more underlying diseases accurately predict the mortality in AKI positive ICU patients.