Mechanical ventilation is a therapeutic modality which is commonly used to support patients with life-threatening illnesses. Weaning from mechanical ventilation is an essential element in the care of mechanical ventilated patient. Repeated ventilator weaning failure can cause prolonged mechanical ventilation period which may increase morbidity and mortality of patients. Aim of the study: To assess factors affecting on the duration of Ventilation among Mechanically Ventilated Patients. Research design: A descriptive exploratory design was used. Setting: Study was conducted at General intensive care units and cardiopulmonary intensive care unit of Damanhur Medical Institute. Methods: A purposive sample of 60 adult patients undergoing Co-ordinated Spontaneous Awakening and Breathing Trials from previously mentioned setting. Tools: Three tools were used included: Spontaneous Awakening Trial Safety Screen, Spontaneous Breathing Trial Safety Screen, Mechanical ventilation duration measurement record. Results: The main factors affecting on the duration of mechanical ventilation were SAT, and SBT co-ordinated protocol before weaning. Conclusion: The highest percentage of patients had short duration of ventilation and safely extubation. Recommendations: Apply Co-ordinated Spontaneous Awakening and Breathing Trials for mechanical ventilated patients help to decrease duration of mechanical ventilation.