Atrial myxoma is the most common benign tumor of the heart. Patients who have atrial myxoma usually present with cardiac obstruction, arrhythmia, or peripheral embolization. We encountered an unusual case of acute upper extremity ischemia due to a massive atrial myxoma in a young man. A 38-year-old man was admitted to our hospital with an acute onset of severe, right upper extremity pain and paralysis while working. Neurologic examination yielded normal results, but the patient showed no palpable right radial or ulnar artery. Routine sonographic evaluation revealed acute aortic embolism in his right brachial artery. Because of his young age and otherwise healthy condition, we decided to perform transthoracic echocardiography, which showed a huge left atrial tumor, which we suspected to be myxoma. We then performed urgent concurrent open heart surgery and embolectomy to avoid further embolism. The microscopic findings of the resected tumor and embolism specimens were myxoma. He was discharged without complications.