We herein report a rare case of intraspinal ectopic endometrial tissue associated with tethered cord syndrome. The patient underwent MR imaging of the lumbar spine and CT spinal angiography. Asymptomatic dysraphism was also detected, including spinal bifida, low-lying conus medullaris, spinal meningocele and a lumbosacral lipoma. Venous reflux obstruction was also suggested. The patient underwent L2-S1 laminectomy and microdecompression of the lesion. The histological and immunohistochemical features were characteristic of ectopic endometrial tissue. Since the surgery, no neurological signs have been noted, either during or outside the patient's menstrual periods. The two-month follow-up MRI scans showed a regression of the lesion.