The authors report on an 81-year-old woman with a primary hydatid cyst located in the posteromedial aspect of the thigh. She presented with sciatica, and the cyst was also associated with neurological dysfunction because of its intra-neural location. Diagnosis of a cyst in a nerve body is very rare, and the one reported here might be the first such case. So far, in all the previously reported cases in which there were also neurological findings, the cysts in the vertebral column were compressing the spinal cord or there was an intrapelvic mass compressing the sciatic nerve. Hydatid cyst should be considered in the differential diagnosis of sciatica, especially when treating patients who live in or have emigrated from areas of the world where Echinococcus granulosus is prevalent.