This study describes a 43-year-old woman with ossification of the posterior longitudinal ligament (OPLL) in the thoracic spine for several years that resulted in the compression of the thoracic spinal cord, causing lower limb paralysis. Posterior laminectomy with decompression was immediately performed for severe spinal stenosis. However, thoracic myelopathy with lower limb paralysis remained postoperatively. After an intensive 2-month rehabilitation therapy, the muscle strength of both lower limbs increased to grade 4, and she could walk with assistance of a quad cane. Activities of daily living and quality of life significantly improved at one-year follow-up. In this case, we discuss postoperative lower limb paralysis and subsequent rehabilitation.