Background and Objectives: The goal of this study was to evaluate the functional outcomes of patient treatment using an allograft after chronic locked posterior shoulder dislocation associated with a bony defect of the upper edge of the humerus that involves 25–50% of the articular surfaces. Materials and Methods: A total of 20 patients were included in this study. Electrocution was the cause of injury in eight patients; in ten patients, the cause was direct trauma; and in two patients, the cause of injury was a fall due to hypoglycemic coma. A standard deltoid pectoral approach was used and a fresh-frozen osteochondral allograft of the femoral condyle was applied. In evaluating the results, Constant’s scoring scale was used. Results: The average value of Constant’s point scale for the operated shoulder is 84.14 points. This result is good according to the average value of Constant’s point scale. Conclusions: Patients with locked chronic posterior dislocation in combination with a bony defect of the humeral head that covers 25–50% of the articular surface, in our opinion, should be treated using bone allografts rather than non-anatomical reconstruction methods.