Background: A high-risk neonate refers to a newborn who has an elevated likelihood of experiencing adverse health outcomes or death, irrespective of their gestational age or birth weight. A mechanical ventilator controls or helps a neonate's respiration when he or she cannot maintain adequate gas exchange because of respiratory or ventilatory failure. Aim of the study: Assess the nurses' knowledge and practices regarding care of high-risk neonates connected with mechanical ventilator. Research design: A descriptive research design was used. Setting: The study was conducted in the Neonatal Intensive Care Unit (NICU) at Minia University Hospital for Obstetrics and Pediatrics. Sample: All the available nurses (40) working in NICU at Minia University Hospital for Obstetrics and Pediatrics. Tools: Tool (I): A structured interview questionnaire covering the demographic characteristics of the studied nurses and nurses' knowledge. Tool (II): Observational checklist sheet. Results: The results of this study proved that; the vast majority of the studied nurses had poor knowledge, and most of them had an incompetent level of total practice regarding the care of high-risk neonates under mechanical ventilator. There is also, a statistically significant relation between the total mean score of nurses' knowledge and practices and their marital status and qualifications. Conclusion: A minority of the studied nurses had average knowledge and competent level of total practices regarding the care of high-risk neonates under mechanical ventilator. Recommendations: Periodical training programs and educational workshops should be conducted for nurses working in the NICU about the nursing care of mechanically ventilated neonates.