Background: Children on mechanical ventilator are totally depended on nurses. So nurses have a major role to play in sustaining the lives of these children by meeting their health requirements. Aim of the study: was to assess nurses' performance regarding care of mechanically ventilated children. A descriptive study design was conducted in pediatric intensive care units in Suez Canal University Hospitals, Ismailia Medical Complex, Pediatric Hospital at Zagazig University Hospitals and Al Ahrar Hospital in Zagazig city. Sample: A purposive sample of 74 nurses.  Tools of data collection: Tool I: A structured interview questionnaire sheet to assess nurses' knowledge regarding care of mechanically ventilated children. Tool II: observational checklist to assess nurses' practice provided to mechanically ventilated children. Results: The results of the present study revealed that less than one fourth of studied nurses had good knowledge, less than one third  of them had fair knowledge, less than half of them had poor knowledge while more than two third of studied nurses had incompetent total practice level. Conclusion: It was concluded that less than half of studied nurses had poor knowledge regarding care of mechanically ventilated children while more than two third of studied nurses practice provided to mechanically ventilated children was incompetent. Recommendations: Based on the results of the present study continuous formal training and educational programs about care of mechanically ventilated children will help nurses to update their knowledge and improve their practice.