Heat stroke is an acute, life-threatening emergency characterized clinically by elevated body temperature and central nervous system dysfunction. The nurse has an important role in critical care team. Therefore, the aim is to evaluate the effect of an educational program on the nurses' performance regarding heat stroke. Quasi-experimental research design was used to conduct this study. This study was carried out at Emergency department and isolation room at Assiut University Hospitals. The sample: A convenient sample included all nurses working at Assuit University Hospital ; 30 nurses in the emergency unit and 12 nurses in isolation room .Tools: Two tools were utilized in this study. Tool I: Nurses' knowledge assessment. Tool II: Nurses’ performance observational checklist questionnaire. Results: The present study revealed that total mean scores of the nurses' knowledge was 13.02±4.49 pre implementation, 27.57±2.38 post implementation of educational program and 26.33±4.06 at follow up. Total mean scores of the nurses’ performance was 112.64±8.84 pre implementation, 177.97±8.35 post implementation of the program and 160.67±14.44 at the follow up .So there is a significant difference between their knowledge before and after the educational program. Conclusion: The study concluded that the educational program led to improvement in nurses' knowledge and performance about heat stroke. Recommendation: The program should be utilized for all new graduated nurses to be orientated to all aspects of care provided for heat stroke patients.