This study reviews a case of sacral fracture with delayed onset neurological deficit that showed good results after decompressive surgery. The delayed neurological deficit appeared at 4 weeks after injury and it was treated with anterior decompression through transperitoneal approach. A 23-year-old woman was injured in a car accident and had bilateral pubic rami fractures and fractures of the sacral ala on the right side. She was treated with external fixation devices for approximately four weeks, but complained of pain and numbness. The dorsiflexion and plantalflexion of the right ankle was weakened and graded as grade 2. Preoperative pelvic and sacral radiographs, computed tomography, magnetic resonance imaging and electromyelography, and nerve conduction study were performed to identify the region of neurological deficit, and we decided to implement neurological decompression. By transperitoneal approach, we performed bone curratage and decompression around the region of sacral alar slope and S1 foramen. The pain and numbness of the right foot cleared up. Dorsiflexion and plantalflexion of the right ankle improved to grade 5. Anterior decompression by transperitoneal approach proved to bring satisfactory results in a patient, who presented delayed neurological deficit after sacral fracture.