Abstract Background Non-invasive ventilation (NIV) is successful as first-line treatment for patients admitted to hospital with hypercapnic respiratory failure due to AECOPD. Significant diaphragmatic muscle dysfunction (DD) exits in different disease-related and physiological conditions, including COPD. Ultrasonography is considered as a non- invasive and bedside method and commonly applied in intensive care unit (ICU) to assess diaphragmatic function. Objective To demonstrate the value of diaphragmatic ultrasound assessment for patients with AECOPD undergoing NIMV. Patients and Methods A population of 24 consecutive patients with AECOPD admitted to Ain Shams University Hospitals’ Intensive Care units (ICU) were enrolled. Change in diaphragmatic thickness fraction (ΔDTF) < 20% and diaphragm excursion< 10 mm during tidal volume was the predefined cut-off for identifying DD. Correlations between ΔDTF < 20%, diaphragm excursion< 10 mm and NIV failure and other clinical outcomes were investigated. Results 24 cases with AECOPD, 33.3% of them (8 cases) had diaphragm dysfunction (DD+) but after NICPAP 2 cases improved and only 6 cases remain with DD and 16 Patients without DD (DD−). DD+ patients had a higher risk for NIV failure than DD−patients (p < 0.011), and this finding was significantly associated with higher in-hospital, and 30-day mortality rates; longer mechanical ventilation duration; higher tracheostomy rate; and longer ICU stay. Conclusion AECOPD patients with diaphragmatic dysfunction as diagnosed by US showed higher incidence of NIMV failure, longer MV, ICU length of stay, In- hospital mortality, ICU and MV duration were significantly longer in group with DD. Insignificant difference was found considering mortality after 30 days in patients with or without diaphragm dysfunction.