Diastematomyelia is an uncommon congenital spinal cord abnormality, which is classically found in females and children. It involves the splitting of the spinal cord, either by a bony spur or by a fibrous septum. Diagnosis is usually made by using radiological investigations such as MRI and CT scans. In this case report, we present a rare case of an adult presenting with symptoms of lower back pain, urinary incontinence, and decreased sensation in the perineum secondary to diastematomyelia. MRI was used for diagnosis and a lower thoracic spinal cord malformation was noted. She failed conservative treatment and was referred for surgery. A large Tarlov cyst was also noted upon operation. She tolerated the operation well and had good motor evoked potentials after the surgery. Moreover, she also reported resolution of bladder function at 3 months follow-up.