Introduction Cerebral metastases are the most common cancer of the central nervous system (CNS). Meningeal infiltration by neoplasms that did not originate in the CNS is a rare fact that is present in 0.02% of the autopsies. Epidemiologically, the radiological presentation mimicking a subdural hematoma is even more uncommon. We report a case of meningeal carcinomatosis by an adenocarcinoma of the prostate mimicking a chronic subdural hematoma. Case Report A 60-year-old male patient was diagnosed with prostate cancer in 2011. He underwent radical resection of the prostate, as well as adjuvant hormonal therapy and chemotherapy. Five years later, the patient presented peripheral facial paralysis that evolved with vomiting and mental confusion. Tomography and magnetic resonance imaging scans confirmed the subdural collection. At surgery, the dura was infiltrated by friable material of difficult hemostasis. The anatomicopathological examination showed atypical epithelial cells. The immunohistochemistry was positive for prostate-specific antigen (PSA) and other keymarkers, and it was conclusive for meningeal carcinomatosis by a prostate adenocarcinoma.