We examined the incidence and predictors of acute kidney injury (AKI) in elderly patients (≥75 years) enrolled in the prospective Italian Elderly acute coronary syndrome (ACS) study and explored the impact of AKI on clinical outcome. Acute kidney injury, defined according to the Acute Kidney Injury Network criteria, occurred in 128 (21%) of 615 patients. Patients submitted to coronary angiographic procedures did not present higher rate of AKI. The only baseline variables independently associated with AKI development were creatinine clearance (odds ratio [OR]: 0.98; 95% confidence interval [CI]: 0.97-0.99) and left ventricular ejection fraction (OR: 0.98; 95% CI: 0.96-0.99). Adverse clinical events were significantly higher in patients who developed AKI. After multivariable adjustment, AKI (hazard ratio: 2.73; 95% CI: 1.87-4.0) was an independent predictor of all-cause mortality within 1 year.