We present a case of traumatic L4-5 bilateral facet dislocation, without neurological deficit, in a 32-year-old female patient, as an unusual seatbelt injury caused by positioning the shoulder harness improperly under her armpit. Open reduction, posterior interbody fusion, and posterior segmental instrumentation were carried out. The aim of this report is to describe this rarely encountered condition and speculate regarding automotive shoulder harness misuse as a potential cause of bilateral locked facet at L4-5, and to emphasize the importance of multidirectional X-ray on first examination. The unusual L4-5 level facet interlocking was attributed to misuse of the automobile shoulder harness. We propose the importance of recognizing this injury and following up on such clues as transverse process fractures and/or widened posterior elements.