Background: Only limited data is present regarding the incidence and prognostic implications of acute kidney injury (AKI) in ST elevation myocardial infarction (STEMI) patients with preserved left ventricular (LV) function in the primary percutaneous coronary intervention (PCI) era. Methods: We conducted a retrospective study of 842 consecutive STEMI patients with preserved LV function (ejection fraction ≥ 50%, assessed by echocardiography) who underwent primary PCI between January 2008 and January 2015. AKI was defined as an increase of ≥ 0.3 mg/dl in serum creatinine within 48 h following admission. Patients were assessed for all-cause mortality up to 5 years. Results: Fifty-two patients (6.2%) developed AKI. Patients with AKI were older, had impaired baseline renal function, and presented more often with heart failure throughout their hospitalization. Patients with AKI had a higher 5-year all-cause mortality (13.4 vs. 2.4%, p < 0.001). Compared to patients with no AKI, the adjusted hazard ratio for all-cause mortality was 2.64 (95% CI 1.25-5.56, p = 0.01). Conclusions: Among STEMI patients with preserved LV function undergoing primary PCI, AKI is associated with a higher long-term mortality.