Valve vegetation is one of the most fearful findings for physicians. The first diagnosis that comes to their mind is infective endocarditis (IE), but it can also be noninfective; nonbacterial thrombotic endocarditis (NBTE). NBTE can be even more challenging than IE for physicians because of the wide range of differential diagnoses such as malignancies, autoimmune disorders and human immunodeficiency virus. A 45-year-old woman presented at the emergency room with a sudden onset of dysarthria and right-sided hemiplegia. Laboratory data showed her blood counts and coagulation test were mostly normal and the magnetic resonance imaging detected a high-signal-intensity change in her left brain. An echocardiogram found a vegetation-like structure on her atrial valve. We highly suspected IE leading to cerebral embolism. The clot was successfully removed by our neurosurgeons and anticoagulation therapy was started concurrently. Her state of consciousness improved, but then she suffered a brain hemorrhage and died. The autopsy revealed that the cause of her vegetation was acute promyelocytic leukemia (APL). Based on these findings, it is important to remember that APL can be the cause of NBTE even if the blood count and coagulation tests are almost normal.