Objective: This study aimed to clarify the practice of in-hospital triage by certified nurses in emergency nursing in the emergency room.Methods: The study conducted semi-structured interview among seven certified nurses in emergency nursing that was followed by qualitative and descriptive analyses.Results: The in-hospital triage included “practices that lead to urgency judgment,” such as interviews to quickly and systematically collect information, reliable observation, and re-evaluation to avoid unexpected changes; “practice for emotional aspects of waiting patients,” where the patient’s state of mind is assessed and a sense of security is provided; “implementation of management,” promote infection control and efficient in-hospital triage; and “utilization of accumulated knowledge and skills.”Conclusions: To practice safe in-hospital triage in crowded and complicated emergency outpatient settings, the “implementation of management” for coordination, collaboration, and leadership among nurses and medical professionals is essential.