A 67-year-old woman was admitted to our hospital for weakness in her right hand. MRI showed multiple cerebral infarctions and ultrasonic cardiography revealed vegetation on her aortic valve, so embolic stroke was diagnosed. Though she was afebrile and her vital signs were normal, chest CT revealed several enlarged mediastinal lymph nodes and a small nodule in the left lower lobe of the lung. Stage III adenocarcinoma of the lung was diagnosed, and the cause of her cerebral infarctions was found to be nonbacterial thrombotic endocarditis (NBTE). NBTE is known as the cause of embolic stroke among patients with advanced cancer, particularly adenocarcinoma. Prompt initiation of continuous heparin administration is required to interrupt the progress of cerebral thromboembolism in NBTE. In cases of coexisting cancer and embolic stroke, we should consider the possibility of NBTE.