Inversion injury of the lateral ankle ligaments is very common. Few studies, however, have focused on avulsion fracture of the lateral ankle ligaments. A fracture producing a small fragment usually avulsed from lateral malleolus and may be easily misdiagnosed as a sprain because the fragment is superimposed on the lateral malleolus and goes undetected on early radiographs, especially in skeletally immature patients. We present a case of isolated avulsion fracture of the talar attachment of the anterior talofibular ligament in 13-year-old male patient. Diagnosis was confirmed by computed tomography and avulsed fragment was fixed to original talar footprint with suture anchors. A high level of suspicion must be maintained to obtain an accurate diagnosis of avulsion fracture in inversion ankle injury because of the high incidence in children and to prevent recurrent instability.