This chapter discusses about the nutrition in a critically ill patients. The primary goal of nutrition support therapy is to supply the substrate necessary to meet the metabolic needs of patients in whom adequate nourishment cannot be provided by mouth. These needs vary with the phase of critical illness. Optimizing nutritional therapy is based on fully understanding the premorbid nutritional status of the patient and the pathophysiology of the underlying critical illness. Oral nutrition support, enteral tube feeding and parenteral nutrition are methods of nutrition support. These methods can improve outcomes, but which of these is more effective and safe can indeed be multifaceted. Enteral nutrition, parenteral nutrition and immunonutrition are general strategy for ICU patients.