Ankle fractures and fracture dislocations are common injuries in orthopaedic practice however pure ankle dislocation without an associated fracture is extremely rare. There are a few cases reporting such a lesion in the literature. Also this injuries are generally open high energy trauma injuries. Closed treatments are reported to be effective and ligament injuries are generally not reported. In this study, we report a closed pure posteromedial ankle dislocation with anterior talofibular ligament rupture and its treatment and outcome in a 12 year-old boy. We think that this is an extremely rare lesion.