The autotransplantation of a third molar represents an alternative treatment solution for filling an edentulous space that may exist because of traumatic avulsion, agenesis, large carious processes, or other reasons, particularly in young patients. Autotransplantation can offer many benefits, including maintenance of a normally functioning periodontium, preservation of pulp vitality, and completion of root formation. This case report describes a successful autotransplantation of an open-apex maxillary third molar germ to replace a hopeless mandibular first molar in a growing patient. After 24 months of follow-up, the donor tooth showed physiological mobility, absence of infection and ankylosis, positive pulp vitality, and fully formed periodontal integration. Radiographic examination confirmed a remarkable radicular edification.