A case of sacral extradural arachnoid cyst associated with lumbar intradural arachnoid cyst in a 35-year-old male is reported. The patient presented with a history of severe sacrococcygeal pain, constipation, and dysuria for several months. Computed tomographic (CT) myelograms and magnetic resonance imaging (MRI) scans showed a huge sacral cyst without neural components. A favorable outcome could be achieved by decompression of the cyst, obliteration of the fistulous channel between the cyst and the thecal sac, and fenestration of the arachnoid cyst into the subarachnoid space. The relevant literatures are also reviewed.