INTRODUCTION: Patients with chronic pulmonary obstructive disease (COPD) are at risk of acute exacerbation. Diaphragm muscle is classically highly solicited in COPD exacerbation. PATIENT CONCERNS: A COPD patient was admitted because of acute dyspnea with wheezing. DIAGNOSIS: acute COPD exacerbation. INTERVENTIONS: A diaphragm ultrasound and a Doppler echocardiography were performed at bedside. OUTCOMES: We measured diaphragm thickening at the apposition zone and diaphragm inspiratory motion from the subcostal view, in addition with classical echocardiographic parameters. CONCLUSION: Despite a normal diaphragm thickening, diaphragm motion during inspiration is reduced in acute COPD exacerbation. These apparently discrepant findings may be explained by the alterations of the respiratory mechanics during COPD exacerbations, which should be considered when evaluating the diaphragmatic function by imaging.