Neutrophil gelatinase-associated lipocalin (NGAL) is a protein of lipocalin family highly expressed in various pathologic states and is an early biomarker of acute kidney injury in cardiac surgery. We performed an observational study to evaluate the role of NGAL in predicting postoperative intensive care stay in high-risk patients undergoing cardiac surgery. We enrolled 27 consecutive patients who underwent high-risk cardiac surgery with cardiopulmonary bypass. Urinary NGAL (uNGAL) was measured before surgery, at intensive care unit (ICU) arrival and 24 h later. Univariate and multivariate predictors of ICU stay were performed. uNGAL was 18.0 (8.7-28.1) ng/mL at baseline, 10.7 (4.35-36.0) ng/mL at ICU arrival and 29.6 (9.65-29.5) 24 h later. The predictors of prolonged ICU stay at the multivariate analysis were body mass index (BMI), uNGAL 24 h after surgery, and aortic cross-clamp time. The predictors of high uNGAL levels 24 h after at a multivariate analysis were preoperative uNGAL and logistic European System for Cardiac Operative Risk Evaluation. At a multivariate analysis the only independent predictors of prolonged ICU stay were BMI, uNGAL 24 h after surgery and aortic cross-clamp time.