Isolated fracture of the calcaneal apophysis is a rare injury in children and adolescents. In this study, we report on a case of a displaced calcaneal apophyseal avulsion fracture in a child treated with open reduction and internal fixation, as well as a review of the literature. A 9-year-old female child presented to the senior surgeon complaining of acute heel pain after a gymnastic injury. She was diagnosed with a displaced, isolated fracture of the proximal calcaneal apophysis for which she underwent open reduction and internal fixation. On the magnetic resonance imaging (MRI) examination, we could diagnose that her injury was not chronic but acute because there was no change of intensity in the metaphyseal area. A combination of bioabsorbable suture tacks and pins was used to anatomically fix the fragment using the tension band wiring technique. At 2 years and 6 months follow-up, she had full range of motion, complete return of strength. We report here on the successful surgical treatment and the first case evaluated by MRI of an avulsion fracture of the calcaneal apophysis in a child.