Introduction: Enteral nutrition delivery is the preferred optimal method of nutritional supplement in patients in the intensive care unit. Aim: This study aimed to compare the effect of early versus late enteral feeding on the outcome of mechanically ventilated patients. Design: A quasi-experimental design. Setting: General, trauma, coronary, anesthesia and obstetric at intensive care units at Assiut university hospital. Subjects: Purposive sample of 80 patients were assigned randomly into two groups: Group1: 40 patients who received enteral nutrition within 24-48hr of ICU admission, and Group2: 40 patients who received enteral nutrition after 48hr of ICU admission. Tools: Patient assessment sheet, Nutritional status assessment tool, Nutritional Intervention Sheet, Acute Physiology and Chronic Health Evaluation (APACHE) II score, and patient outcome assessment tool. Results: There were statistical significant decrease in duration of mechanical ventilation, (4.8±1.65 versus 5.48±1.15), intensive care unit length of stay (5.23±1.66 versus 6.10±2.13), and gastrointestinal tract intolerance (30% versus 62.5%) in early versus late enteral nutrition groups (P value<0.05). Conclusions: Early enteral nutrition group associated with improved outcomes (decrease in duration of mechanical ventilation, intensive care unit length of stay, and gastrointestinal tract intolerance of critically ill mechanically ventilated patients. Recommendation: Provide in-service education and training program for critical care nurses regarding applying early enteral nutrition on critically ill patients.