BACKGROUND Caudal epidural sacral injection is one of the most common conservative treatments for chronic low back pain with radiculopathy. Neurological deficit after injection is a rare complication that must be identified and treated properly. METHODS We report a case of cauda equina syndrome that persisted until 3 months after injection. A 63-year-old man came to our department with severe lumbar canal stenosis who experienced motor weakness, buttocks numbness and voiding difficulties immediately after injection. His lower extremities improved after 24 h, but his neurogenic bladder problems and perianal numbness still persisted. We collaborated with our interdisciplinary teams to do a rehabilitation program, and the symptoms were alleviated and he fully recovered within three months. CONCLUSIONS Patients with severe stenosis can be best described from magnetic resonance imagery scans, and clinicians should be careful about the risks after injection ranging from transient complications to persistent spinal cord injury.