A 77-year-old woman was found accidentally to be in atrial fibrillation. Two-dimensional echocardiography revealed the presence of a mass attached to the anterior papillary muscle of the mitral valve. She was mildly symptomatic for dyspnea and asthenia. The patient was successfully operated on to excise the left ventricular mass and preserve the mitral valve apparatus. Morphological examination of the excised tissue led to a diagnosis of papillary fibroelastoma. Surgical treatment must be considered when such a tumor is diagnosed, even though asymptomatic, and especially if left-sided because of the high risk of systemic embolization.