A 34-year-old man presented with a 15-month history of pain along the left sciatic nerve. Radiographs and computed tomography (CT) revealed an exostosis on the postero-inferior aspect of the left femoral neck. Ultrasonographic examination of left upper thigh and a pelvic magnetic resonance (MR) imaging showed an enlarged sciatic nerve adjacent to the exostosis. Although peroneal and ulnar neuropathies due to the compression by exostosis are reported frequently, imaging findings of sciatic nerve involvement were not well documented in the literature. Multidetector CT and MR findings of a sciatic nerve compression caused by a femoral neck exostosis were presented.