We presented the case of a 60-year-old man with an unexpected complication of acromial osteolysis with subsequent regeneration of the acromion. To our knowledge, this case report represents the first description of the regeneration of acromion after osteolysis. He underwent open reduction and internal fixation with a novel hybrid hook locking compression plate 6 days after the injury. No procedure was undertaken for the coracoclavicular ligament in this case. Five months after internal fixation with a hook plate, the patient underwent surgery for the removal of the hook plate. Radiographs after removal of the hook plate showed erosion of the acromion. We decided to perform a conservative treatment for acromion osteolysis and observed the progress. A final radiograph that was obtained 10 months after hook plate removal shows regeneration of the acromion. We thought that the periosteum played a significant role in the acromion regeneration despite no special treatment.