Introduction: Nutritional support for children who are being seriously unwell has not thoroughly studied and is a contentious issue in Intensive pediatric care. Infants and children who are critically ill lack clear guidelines regarding the best type of nutrition to provide at what time. Objectives: toassess the nutritional status of our patients during time of hospital stay, in critically ill children to investigate significance of nutritional condition on the effect of admission on length of stay of mechanical ventilation (MV) and to assess how mechanical ventilation affect the nutritional status of critically ill patients. Methods: Sixty-four newborns and young children who were brought to PICU and required mechanical breathing were subjects of this research. Cases that required mechanical ventilation and were admitted to the PICU were included. Known malnutrition and cases with dehydration were excluded. Results: There was significant difference between different Subjective Global Assessment (SGA) nutritional score groups and time to reach full caloric requirement with higher mean time in malnourished group and this indicates that the early nutrition leads to good outcome and needs less time to reach full caloric requirement. There was statistically significant difference between different SGA Nutritional score groups and ventilation duration with higher mean duration was in malnourished group and this mean that children who were underweight needed to be on mechanical ventilation support for longer. Conclusion: Anthropometric parameters weight-age z score, height-age z score, MAC-age z score and calf circumference Z score were able to predict mechanical ventilation duration.