: Deep vein thrombosis (DVT), a frequent complication of spinal cord injury, is occasionally caused by neurogenic heterotopic ossification (NHO). In most cases of NHO, the hip joint is affected. Herein, we present a case of paraplegia following radiation-induced myelopathy that presented with left leg swelling due to DVT in the common iliac vein (CIV) caused by venous compression by NHO on the anterior lower lumbar spine. : A 28-year-old man with complete paraplegia due to radiation-induced myelopathy presented with left lower extremity swelling 6 years after the onset of paraplegia. DVT in the left CIV was observed on computed tomography venography. The left CIV was significantly compressed between the NHO at the anterior longitudinal ligament of the lumbar spine and the right common iliac artery, suggestive of May-Thurner syndrome. Slightly distal to that compressed area, the left CIV was significantly compressed by the large NHO at the anterior longitudinal ligament of the lumbar spine. : We believe that such compression of the left CIV would have contributed to the development of DVT. This case shows that DVT might be caused by NHO at the anterior aspect of the lumbar vertebral body, and this may help clinicians identify the main cause of DVT in the leg.