Abstract Background: Mechanical ventilation (MV) is the most used short-term life support technique worldwide and is applied daily for a broad spectrum of indications. It has been shown that mechanically ventilated (ICU) patients may also experience diaphragm weakness and atrophy, which may cause difficult weaning and increased duration of MV. Aim of Study: The aim of this study was to measure the acute effect of transcutaneous electrical diaphragmatic stim-ulation (TEDS) on arterial blood gases (ABG) in mechanically ventilated patients. Patients and Methods: Thirty mechanically ventilated male patients were included in this study. they were recruited from intensive care unit, Cairo University Hospitals. Their ages range from (40-55 years). Patients were assigned into 2 equal groups at random, study group and control group. The study group received one session oftranscutaneous electrical diaphragmatic stimulation (TEDS). Evaluation was carried out before and after the treatment session. The control group was evaluated twice without receiving the treatment. All the patients were assessed by blood gas analysis before and after the treatment. Results: The results of this study revealed thatthere was a significant difference in pH, SaO2 and PaO2/FiO2 ratio between pre & post measurments for study group compared to control group. There was also a significant difference in PaO2 in both groups. The percentage of change was 27% and 13% in favor of TEDS group. However, there was no signif-icant difference in PaCO2 and HCO3. Conclusion: Transcutaneous electrical diaphragmatic stimulation led to immediate improvement in PaO2, pH, SaO2 and PaO2/FiO2 ratio. This finding suggests improvement in oxygenation in mechanically ventilated patients treated with TEDS.