Acute traumatic spondylolisthesis in the lumbosacral spine is an uncommon injury. Traumatic dislocation of the fourth lumbar vertebra over the fifth lumbar vertebra (L4/L5) is extremely rare since few studies have been reported in the current literature. We report on a 53-year-old man, who had a motor vehicle accident and sustained an injury of the lumbar spine without neurological impairment. The radiographic evaluation disclosed an L4/L5 traumatic spondylolisthesis, classified as Meyerding grade III without any fracture of the posterior vertebral elements. To the best of our knowledge, this is the sixth case of L4 traumatic spondylolisthesis without concomitant fracture of the posterior vertebral elements and the third case without any neurological deficit among them. The patient underwent open reduction and posterior instrumentation. Intraoperatively, the posterior ligamentous complex, the capsules of the facet joints and also the disc were found torn, although facets, neural arch, and pedicles were intact. Following decompression and reduction of the spondylolisthesis without any neurologic complications, we performed pedicle screws and rods fixation from the third to the fifth lumbar vertebra (L3-L5). The patient had an uneventful recovery and returned to his previous activity three months after surgery. The four-year follow-up evaluation showed normal spinal alignment, successful pain-free fusion without neurologic complications. Flexion/distraction injury without simultaneous rotation at the L4/L5 segment during traffic accidents or the fall of a heavy object on the bent back accompanied with posterior ligament weakness is thought to be the probable mechanism for this type of injury. Concomitant neurologic impairment is associated with the majority of L4/L5 spondylolisthesis cases. Posterior decompression, reduction, and posterior instrumentation enhances bony fusion, improves the patient’s neurologic status and restores the sagittal alignment.