A middle aged female presented with low back pain for ten years and had tingling and numbness of both lower limbs for last two years. She was investigated and MRI revealed a mass at the dorsal region (D8, D9 level) which was extradural in location. Lesion was compressing the cord. After total removal of the mass, histopathology revealed it to be an arachnoid cyst. As per review of literature, 41 cases of extradural arachnoid cysts are reported. Most of them are located in inferior thoracic region and 4 cases in cervicothoracic region. The pathogenesis, aetiology, and treatment of the spinal arachnoid cyst have not been well documented because of its rarity. The case is discussed in light of the relevant literature.