Acute kidney injury (AKI) following cardiac surgery is a continuing source of morbidity and mortality. Although several studies have attempted to determine its etiology and prophylactic measures, limited data exist after thoracic aortic surgery. The aim of this study was to evaluate the incidence and predictors of AKI in patients undergoing aortic root replacement (ARR) with valve conduit for ascending aorta aneurysms. A multi-center observational study of 414 patients undergoing ARR with a valve conduit was conducted, focusing on clinical outcome and AKI defined by consensus RIFLE (risk, injury, failure, loss of function, end-stage renal disease) criteria. Mean age was 62.5 years (range: 21–82 years) with 327 males (79%). Emergent operations were performed in 5% of the cases, while concomitant surgical procedures were performed in 24.9%. Postoperative AKI (all RIFLE classes) occurred in 69 (16.7%) patients, while eight (1.9%) required dialysis. Independent AKI predictors were packed red blood cells (pRBCs) >4 units (OR 2.28; 95% CI 1.20–4.30), cardiopulmonary bypass (CPB) time longer than 180 min (OR, 2.08; 95% CI, 1.16–3.73), and concomitant surgical procedures (OR, 1.85; 95% CI, 1.04–3.29). The severity of RIFLE class was associated with longer ICU stay, hospitalization, and higher hospital mortality (p < 0.001 for each variable). AKI after ARR operations with valve conduit for ascending aorta aneurysms increases utilization of health resources and is associated with adverse events. Concomitant surgical procedures, prolonged CPB-time, and pRBCs >4 units as independent AKI predictors merit further researches enhancing possible preventive strategies.