The purpose of this retrospective study was to determine the incidence of and risk factors for delirium in patients undergoing cardiac surgery. In addition, the influence of different post-surgical intensive care unit (leU) environments on delirium incidence was also studied. A detailed clinical report form was created to collect pertinent data in order to determine the effect of pre-operative, intraoperative and postoperative variables on delirium. Our study identified several risk factors for an increased incidence of delirium: hypertension, preoperative statin use, coronary artery bypass graft (CABO) surgery, aortic valve surgery, advanced age, prolonged bypass time and lowest serum sodium value during surgery. Extubation in the OR was associated with a lower incidence of delirium. In our comparison of the different ICU environments, in the first cohort (environment #1), 19.2% of patients experienced at least one episode of delirium. In the second cohort (environment #2; enhanced by privacy, reduced noise, and natural light), the incidence was reduced to I 1.1 % (p = 0.0582). As the two cohorts had otherwise similar demographics and other perioperative characteristics, it is likely that the reduced incidence of delirium was attributable to the enhanced ICU environment.