OBJECTIVE Pain arising in the lumbar spine can have many etiologies, nearly 80% of which cannot be established with certainty. We present a very rare cause of back pain. METHODS A 54-year-old woman presented with a 2-month history of low-back pain and right-sided sciatica. Conventional analgesics, physiotherapy, and epidural steroid application had failed to provide relief. She had tenderness of the right sacroiliac joint. Diagnostic fluoroscopic-guided sacroiliac-joint injection with lidocaine did not produce symptomatic relief. Pelvic ultrasonography and magnetic resonance imaging showed septated multilocular hydatic cysts along the sciatic nerve. Surgical exploration noted multicystic lesions along the sciatic nerve woven to the nerve. Her low-back pain disappeared completely after the operation. She received oral albendazole for 6 months to prevent any recurrence of the disease and remains asymptomatic. CONCLUSIONS Hydatid cyst can be included in the differential diagnosis of lumbar back pain, especially in the endemic areas.