Background: Nurses should be highly knowledgeable and qualified to care for patients in emergencies. Therefore, updating nurse's knowledge and practices of triage application has a significant role in the reduction of mortality rates within emergency departments. The aim of the study: Assessment of Critical care nurses' knowledge and practices of emergency triage. Design: A descriptive exploratory research design was used in the conduction of this study. Setting: This study will be carried out in emergency departments at Assuit University (Trauma Unit) and emergency departments at Hurgada General Hospital Sample: A convenient sample of all nurses in emergency departments was included in the study. Tools: The study tools were composed of mainly two tools: Tool I: Nurse's knowledge assessment questionnaire, which consists of two parts: Part I: Emergency nurse's sociodemographic data and Part II: Emergency Nurse's knowledge of triage system. Tool II: Emergency nurse's performance assessment checklist. Method: The researcher used the preparatory phase and assessment phase for the implementation of the study. Results: Results showed that Nurses lack of Knowledge (56.7%) and performance regarding the application of triage within emergency departments. Conclusion: Most of the nurses working within the emergency departments have almost low level of knowledge and practices regarding the implementation of triage within emergency departments, so different facilities should have a plan for upgrading the Nurse's knowledge and practices of triage application. Recommendations: Hospital management should focus on the importance of triage application in saving patient's lives and decreasing the workload of ER healthcare providers.