Dural metastases are uncommon in cancer patients, but can have as much of an effect on the lives of patients as brain metastases. Dural metastases are most commonly associated with primary cancers of the breast, prostate, and lung, and it is rare that the primary site of the tumor is unknown. In this study, we encountered a 51-year-old woman who had developed multiple bone tumors, with no known primary cancer lesion. A tumor biopsy of the sacral bone revealed non-keratinizing squamous cell carcinoma; the patient was therefore diagnosed as having multiple bone metastases of an unknown primary cancer. Magnetic resonance imaging revealed cranial metastases and partial thickening of the dura with suspected dura metastases. Platinum-based chemotherapy reduced the bone metastases and the thickened dura. However, as resistance to chemotherapy developed, invasions progressed rapidly and diffusely throughout the dura. This was accompanied by the development of dysarthria, visual impairments, and delirium. The patient died 10 months after being diagnosed with dural metastases. This report provides information on the clinical course and prognosis of patients with dural metastases of unknown primary cancer. Furthermore, it may help to construct a treatment strategy for dural metastases.