A 62-year-old male developed headache, restlessness and left hemiparesis three months after being diagnosed with advanced lung cancer. Computed tomography on admission revealed a crescent-shaped, mixed intensity area in the right fronto-parietal subdural region and multiple tumors in the brain parenchyma. Under a diagnosis of chronic subdural hematoma and multiple brain metastases due to lung carcinoma, burr hole irrigation was performed. Adenocarcinoma cells were found in the dura matter and hematoma. Nontraumatic chronic subdural hematoma secondary to dural metastasis is a very rare condition. Only 52 cases of such spontaneous subdural hematoma have been reported. We describe the clinical features and discuss the mechanism referring to the pertinent literature.