We report a case of a fast-growing cardiac papillary fibroelastoma (CPF) arising in the aortic valve. A 71-year-old woman was referred to a cardiologist for investigation of palpitations. Cardiac catheterization, coronary angiography, and echocardiography showed no stenosis of the coronary arteries, nor any other cardiovascular abnormalities. However, 12 months later she was referred to our hospital for further investigations when she began experiencing chest discomfort on exertion. This time, echocardiography showed an abnormal mass arising from the aortic valve, floating between the left sinus of Valsalva and the ascending aorta. Considering the risk of an embolic event, we performed semi-emergency surgery to remove the tumor, preserving the aortic valve. The resected tumor was 16 x 7 mm, and sea anemone-like, with many villus projections. It was diagnosed as papillary fibroelastoma. Such rapid development of CPF is rare.