Primary diffuse meningeal melanomatosis can clinically mimic a wide variety of other conditions, including lymphoma, leukemia, neurosarcoidosis, metastatic carcinoma, acute disseminated encephalomyelitis, subacute meningitis, viral encephalitis, and idiopathic hypertrophic cranial pachymeningitis. We report on a young patient with primary diffuse meningeal melanomatosis who presented with papilledema, flaccid paraparesis, and cognitive impairment. The importance of imaging of the whole central nervous system, cerebrospinal fluid analysis, and pathohistological examination is emphasized in making the appropriate diagnosis.