Objective This study aimed to identify the core symptoms of delirium, particularly in elderly people associated with major risk factors, using the Korean version of the Delirium Rating Scale-Revised-98. Methods The study sample consisted of 200 patients (mean age: 72.7±3.9 years, male: 68.5%) who had been diagnosed with delirium. Exploratory factor analysis was used to investigate the factor structure, and confirmatory factor analysis was used to evaluate the goodness of fit of the results. Results The results demonstrated three core domains of delirium in the elderly patients: 1) the cognitive domain (e.g., language, thought process, orientation, attention, long-term memory, and visuospatial ability); 2) the circadian domain (e.g., sleep-wake cycle and motor behavior); and 3) the short-term memory domain (short-term memory). These results were confirmed by confirmatory factor analysis. Conclusion The findings of this study suggest a theoretical domain structure for delirium in elderly patients.