A disc cyst is a rare entity with a clinical presentation that closely mimics an intervertebral disc herniation. Disc cysts are ventrally located, intraspinal, extradural cystic lesions that communicate with the parent intervertebral disc through a ruptured annulus. We present the clinical features, magnetic resonance imaging, intra-operative and histopathological findings of a variant of a lumbar intervertebral disc cyst in a 13-year-old girl who presented with a 6-month history of unilateral radiculopathy following an injury. Magnetic resonance imaging revealed a large posterocentral, fluid-filled cyst occupying the L5-S1 interspace and bulging into the spinal canal. The cyst was confined within an intact bulging annulus fibrosis and extended directly from the parent disc. The cyst was surgically decompressed, resulting in complete symptomatic relief.