Background: Delirium is a clinical condition characterized by an acute change in brain function and is frequently observed in critically ill patients. The condition has been associated with negative outcomes, making it crucial to identify patients who are at risk. Two recent prediction models have been developed to estimate the risk of delirium in intensive care unit (ICU) patients; the prediction model for delirium (PRE-DELIRIC) and the early prediction model for delirium (E-PRE-DELIRIC). We aimed to perform an external validation of these models in a Danish cohort of critically ill patients. Methods: We conducted a prospective, observational multicenter study to validate the PRE-DELIRIC and E-PRE-DELIRIC models in a population of patients admitted to four general ICUs in the Zealand Region of Denmark. From January 2022 to January 2023 all adult patients acutely admitted to the participating ICUs were assessed for eligibility. Patients had to be admitted to the ICU for >24 h to be included in the study. Included patients were screened with E-PRE-DELIRIC upon ICU admission and PRE-DELIRIC after 24 h of admission and followed throughout their ICU stay with CAM-ICU delirium assessments. Our primary outcomes were the prognostic accuracy measured by Area Under the Receiver Operating Characteristics (AUROC) and the calibration plot for the E-PRE-DELIRIC and PRE-DELIRIC prediction models. Results: We included 660 patients, of whom 660 were assessed with E-PRE-DELIRIC, and 622 were assessed with PRE-DELIRIC. PRE-DELIRIC showed acceptable discrimination with AUROC of 0.70 (95% CI 0.66 to 0.74) and good calibration. E-PRE-DELIRIC had inadequate discrimination AUROC of 0.63 (95% CI 0.58 to 0.67) and poor calibration. Conclusion: In a Danish cohort, we found that the PRE-DELIRIC model demonstrated acceptable performance and E-PRE-DELIRIC demonstrated poor performance. In critically ill adult patients PRE-DELIRIC may be useful in identifying patients at high risk of delirium.