Background; Critically ill children have a high incidence of malnutrition on admission to the pediatric intensive care unit and low metabolic reserves. The aim of this study was to assess nutritional support to pediatric critically ill patients admitted to Pediatric Intensive Care Unit (PICU) and its correlation with their outcome as regarding to need for mechanical ventilation, acquired infection, metabolic complications, and mortality. Methods; This study was conducted on 75 pediatric critically ill patients admitted to PICU, 25 patients were supported by enteral nutrition. 25 patients with inadequate enteral nutrition were supported by complementary parenteral nutrition and 25 patients were supported by total parenteral nutrition due to their contraindications to EN.All included patients were subjected to full history taking, thorough clinical examination , laboratory investigations were done :complete blood picture, serum electrolytes (Na, K, Ca, Po4 and Mg), renal functions, liver functions, serum albumin and C reactive protein. Results; only 73.3% of patients in enteral nutrition group and 83.3% of complementary parenteral nutrition reach target calories on discharge from PICU in contrast to total parenteral nutrition group as all patients reach target caloric requirements on discharge from PICU.There were significant higher prevalence of metabolic complication, need of mechanical ventilation, mortality and higher mean values of length of hospital stay among high malnutrition risk cases. Conclusion; achievement of target caloric requirements during PICU stay improves outcome as regard need for mechanical ventilation, length of hospital stay and mortality, regardless of route of nutritional support.