Fever of unknown origin may present diagnostic and/or curative difficulties. Myxomas are one of the rare causes of fever of unknown origin. A 67-year-old man with a 4-month history of fever of unknown origin was admitted to our department. Physical examination revealed 38.4°C axillary temperature and accentuated second heart sound in cardiac auscultation. Blood, urinary, and throat cultures were negative. Transesophageal echocardiography showed a left atrial mass partially prolapsing into the left ventricle during diastole. Left atrial mass was excised, and histological examination showed atrial myxoma. Fever resolved within 48 hours after the operation, and the patient was discharged from hospital with complete improvement.