Background: Diaphragm dysfunction (DD) is frequently seen in critically ill patients, and ultrasound could be a useful tool to detect it and to predict extubation success or failure in mechanically ventilated patients. Besides, it would also be useful in differential diagnosis of dyspnea and respiratory failure. Aim of work :The aim of work is to evaluate usefulness and accuracy of ultrasound in assessment of DD in intensive care unit (ICU) patients in comparison with clinical outcome of patients.. In this prospective study, we compared the performance of ultrasound in visualization of diaphragm, detection of paradoxical movement, measurement of tidal and maximal thickness, and excursion, and calculation of thickening fraction (TF) of the diaphragm in quiet breathing. Patients and Method: The present study was performed on50 patients (26 males and 24 females) admitted in RICU in Benha university hospital The field study was conducted from March 2019 to September 2019. Ultrasound of the Rt, hemidiaphragm was done on the day of admission or soon after admission (1-2) days. Results: there was no statistical significant difference between the studied groups regarding ultrasound measurement (DTF, DE and DT) and patient outcome with p value (0.273,0.245 and 0.497)respectively.Conclusion: ultrasound of diaphragm in ICU patients may be a reliable, noninvasive and convenient way to assess the DD in ICU patients to predict their outcome.