Purpose: Screening of delirium using delirium assessment tools could promote delirium detection, however,there is lack of report about regular delirium assessment in Korea. This study was intended to describe theprevalence and related risk factors of delirium in intensive care unit (ICU). Methods: The Confusion AssessmentMethod for the ICU (CAM-ICU) data which were evaluated by nurses in ICUs was obtained through retrospectivechart review. Data were analyzed using descriptive statistics, Chi-square test, t-test, Mann-Whitney U test, andstepwise logistic regression. Results: Delirium was evaluated in 125 patients. The incidence rate of delirium was27.2% with a high prevalence of hypoactive delirium compared to hyperactive delirium (61.8 vs. 38.2%). Thosewith delirium were older, had hypertension, stayed longer in hospital, receiving ventilator support, had morenumber of catheters, had low serum protein and albumin level. Delirium incidence also varied according todiagnosis. Age, diagnosis of gastrointestinal disease, and application of ventilator were the significant risk factorsfor the incidence of delirium. Conclusion: Routine delirium screening is important for early detection ofdelirium. Identification of high-risk group and running delirium prevention programs could improve earlyrecognition of delirium in ICU.