Acute traumatic spondylolisthesis at L5-S1 level is a rare condition, almost exclusively the result of major trauma, frequently associated with transverse process fractures and severe neurologic deficits. Recently, open reduction and internal fixation with posterior stabilization has been the method of treatment most frequently reported. We report a rare case of traumatic L5-S1 spondylolisthesis with a unilateral facet locking with a review of literatures.