Objective: The purpose of this study was to investigate agreement among triage nurses and emergency physicians regarding triage decisions, and relevant factors that affect triage decisions of nurses at the emergency department of a regional hospital in Hualien, Taiwan. Patients and Methods: A prospective approach was used to collect data on triage category judgements from nurses and physicians. A questionnaire was used to obtain triage nurses’ demographic data. All data were analyzed by using SPSS statistical software. Results: Totally 4105 patients were triaged. The triage nurses’ judgements of urgency categories were compared with those of emergency physicians. The results revealed that inter-observer agreement was 85%, kappa=0.061. Four percent of patients were overtriaged, and 11% were undertriaged, especially emergency and urgent patients, by triage nurses. Conclusions: These findings suggest that improvement in triage nurses’ assessment ability with acute and critical patients is needed in order to improve emergency care. In addition, the proportion of nurses-physician agreements among nurses with over 2 years of emergency experience was significantly higher than for those with under 2 years of experience. Finally, several recommendations are made regarding nursing practice, nursing education, and nursing administration, as well as directions for future studies.