Ectopic adrenal cortical neoplasms are extremely rare. The authors describe their own case of intradural, extramedullary conus medullaris adenoma that occurred in a 55-year-old woman, which was clinically accompanied by lumbar pains, left leg numbness, and left foot weakness during 10 years. The mass was histologically composed of rounded and polygonal cell fields with rounded, regular nuclei and abundant eosinophilic and clear cytoplasm. There were no necroses or mitoses. The cells were immunohistochemically positive for cytokeratin AE1/3, vimentin, inhibin-α, melan-A, and synaptophysin. An ectopic adrenocortical adenoma was diagnosed after ruling out myxopapillary ependymoma, meningioma with oncocytic transformation, paraganglioma, metastatic renal cell carcinoma, and adrenal cortical carcinoma. In the opinion of most investigators, extra-adrenal tumors develop from ectopic adrenal cortical tissue. To date, only eight intraspinal adrenal cortical tumors have been described. These tumors should be considered in the differential diagnosis of central nervous system masses located in the lower spinal canal.