A previously healthy 43-year-old man presented with durable occipitalgia for 1 month. Neurological examination revealed severe pain in the right C2 area accompanied by neck stiffness. Magnetic resonance imaging revealed an enhancing, polycystic intradural mass at the C2 level, occupying the left dorsolateral part of the spinal canal. In addition, a rim-like enhancement was found along the surfaces of the spinal cord. Blood tests did not show signs of infection. A lumbar spinal tap revealed albuminocytologic dissociation without cultured organisms. Cranial computed tomography scans taken 20 days later revealed an overt ventriculomegaly. The patient underwent a total tumor resection through hemilaminectomy of the C2. Intraoperatively, the left dorsal C2 roots were found to be extremely redundant due to the tumor and surrounding thickened arachnoids. The roots restored normal morphologies after resection of the arachnoids and tumor. Postoperatively, the patient's symptoms resolved and histological diagnosis was endodermal cyst. Four weeks later, a ventriculoperitoneal shunt was placed to treat progressive ventriculomegaly. A polycystic intradural mass of the upper cervical spine should assume an endodermal cyst that may cause contralateral occipitalgia and aseptic meningitis.