BACKGROUND Sudden onset of chest wall bulging is a rare chief symptom in the emergency department (ED). However, it may represent life-threatening diseases, such as tumor bleeding, aneurysm rupture, or subcutaneous emphysema. METHODS We present an 89-year-old woman who visited our ED with a chief symptom of abrupt bulging of the right chest wall accompanied with severe pain. The patient had a history of peripheral artery disease and 10-year post-extra-anatomical axillo-femoral bypass (AxFB) status. After several examinations, the patient was diagnosed as having spontaneous pseudo-aneurysm rupture of an extra-anatomical AxFB graft. Emergency endovascular intervention with stent insertion was performed immediately, and the patient was eventually discharged successfully. WHY SHOULD EMERGENCY PHYSICIANS BE AWARE OF THIS?: Although spontaneous pseudo-aneurysm rupture of an extra-anatomical AxFB graft is rare, the disease may consequently lead to a fatal outcome once misdiagnosed, and prompt intervention is warranted. Therefore, we should always consider the differential diagnosis of this disease in patients with a bulging chest wall and history of AxFB graft placement.