Nurses play a critical role of in pediatric emergency care units (PEUs) as recommended by Emergency Nurses Association (ENA). So, they should have essential and updated information. The aim of the current study was to evaluate the effect of designed training intervention program on nurses' performance regarding care of seriously sick children at Pediatric Emergency Department. A quasi- experimental research design was utilized to conduct the current study at Pediatric emergency units at Benha university hospital and Benha Specialized pediatric Hospital. Subjects: A convenient sample of 50 nurses and children who admitted to emergency units were recruited in this study. Tools: Three tools were utilized for data collection. A structured interviewing questionnaire sheet, nurses' practice observational checklist and likert attitude scale. Results: It was evident from the results of the current study that, nurses' total knowledge mean scores were higher post program implementation compared with preprogram implementation and total practice scores were improved on post program test compared with pre program test. There was a statistically significant positive correlation (P<0.001) between total knowledge and total practice on pre and post program phases. Conclusion: Based on the results of the present study, it can be concluded that, the designed training intervention program was effective in improving nurses' knowledge and practice regarding emergency care of seriously sick children. Reflecting on decreasing waiting time at emergency care departments. Recommendations: Continuous in-service training for nurses through educational programs mustbe established. In addition, pediatric emergency care must be incorporated in nursing education curriculum especially in the undergraduate nursing studies.