Background: Mechanical ventilation(MV) is a major factor in the care of patients in critical conditions that is used to create better conditions for gas exchange at the alveolar surface and tissue through improvement and facilitating the entry and exit of the air. Although MV therapy is crucial, but brings different experiences of physical and psychological stress for the patient as well Using lavender essential oil is considered one of the complementary therapy and was reported to be effective in improving MV weaning outcomes. The aim of the study was to evaluate the effect of lavender oil on vital signs among mechanically ventilated patients. Design: a quasi-experimental study. Setting :the study was carried out at general ICUs of Tanta University Emergency Hospital. subjects: a purposive sample of 60 adult patients from both genders newly admitted attached with mechanical ventilator was involved in this study. Data collection tool: Integrated Nursing Practice & weaning trial assessment tool was used to collect data. Results: There was statistically significant difference between control and study groups before and after application of lavender oil regarding(body temperature, HR, RR, and SPO2). Conclusion: Implementation of lavender oil has been shown to enhance mechanically ventilated patients outcomes. It is associated with significant improvement of vital signs, oxygenation and mean arterial blood pressure. Recommendation: this study recommends the importance of implementation of lavender oil using massage and inhalation techniques for mechanically ventilate patients.