Background: Delirium is a temporary mental disorder, which occurs frequently among patients who undergo cardiac surgery. Delirium prediction and its associated prevention is essential. In a previous study, a risk checklist for delirium was developed. Aims: The present study validated this checklist in a new, larger study population, and also investigated new risk factors. Methods: Risk factors were obtained during the preoperative outpatient screening in 300 patients who underwent elective cardiac surgery. The Delirium Observation Screening scale was utilized pre- and postoperatively to assess delirium. Results and Conclusion: The incidence of delirium was 17.3%. A higher Euroscore, but not a disturbance in electrolytes, was confirmed as a predictor of postoperative delirium. Based on this study, a new risk model was constructed with the following risk factors: a higher Euroscore, older age (≥70 years), cognitive impairment, number of comorbidities, history of delirium, alcohol use and type of surgery. When using a probability of delirium of 20%, as predicted by the model, the sensitivity was 80.8% and the specificity 82.2%. The area under the curve was 0.89. With the revised delirium risk checklist, including seven new risk factors, patients with an increased risk of developing delirium following cardiac surgery could be identified more accurately.