A 59-year-old man who was diagnosed with hypertension and a large thoracoabdominal aortic aneurysm was referred to our hospital for surgical treatment. He underwent open surgery and thoracic endovascular aneurysm repair in three stages. He developed paraplegia after the third surgery. Despite acute postoperative treatment and rehabilitation, his lower extremity motor function and bladder and bowel dysfunction did not improve. He was transferred to a recovery hospital 67 days after the third surgery. However, he was readmitted to our hospital about four months later for management of a refractory decubitus ulcer and recurrent urinary tract infections. Computed tomography revealed hematoma and calcification around the femur. Based on the clinical course and imaging findings, we diagnosed neurogenic heterotopic ossification associated with postoperative paraplegia in this patient. He had flap reconstruction for the ulcer. Finally, he was discharged 79 days after readmission. To date, no study has reported neurogenic heterotopic ossification associated with postoperative aortic aneurysm paraplegia. The mechanism underlying this condition is similar to the widely accepted process associated with traumatic spinal cord injury, and conservative treatment comprising pressure ulcer treatment and antibiotics was continued. Although acute rehabilitation is important after highly invasive aortic aneurysm surgery, rehabilitation is limited by the risk of neurogenic heterotopic ossification in patients with postoperative paraplegia, and recovery and maintenance of activities of daily living are challenging. To our knowledge, early diagnosis and prompt treatment for these complications are important considering neurogenic heterotopic ossification.