Spinal canal extradural arachnoid cyst is an uncommon, expanding lesion which may communicate with the subarachnoid space. They may be either intra or extradural with intradural cysts being less common. Spinal arachnoid cysts are usually in the thoracic spine, and they may cause symptoms due to spinal cord compression. Although surgery is the preferred way of management, there are reported cases with long term follow-up in the literature. Here we present a 14-year-old female who presented with intermittent low back pain for 1 year and a spinal arachnoid cyst that was followed for two years without any neurological deterioration.