Among the many causes of sciatica, endometriosis, a rare aetiology, should be considered in menstruating women in view of the diagnostic strategy and ensuing therapeutic implications. We report a case of sciatic nerve involvement with endometriosis in contact with the nerve in the left sciatic notch. Exploration by MRI was invaluable for the diagnosis, revealing a signal on the stem of the nerve suggestive of a lesion with haemorrhagic content.