The occurrence of complications of fracture healing, such as delayed union and nonunion, is well known, but the use of pharmacotherapy for these delayed unions and nonunions has not been explored in detail. The authors describe a case of traumatic humeral shaft fracture successfully treated with once-daily administration of 20mcg of teriparatide for six months. The patient was a 22-year-old male who had been through a road traffic accident. The radiograph of the humerus shaft showed a fracture line and the displaced distal portion of the shaft of the humerus. Based on these features, the patient was diagnosed with a humeral shaft fracture. The patient underwent internal fixation with a dynamic compression plate. However, there were no signs of callus formation even after 12 weeks from the time of internal fixation. The patient was initiated with teriparatide administration and union was achieved after six months of a once-daily administration of teriparatide. Once-daily teriparatide treatment is shown to be beneficial for improving the healing of humeral shaft fractures showing delayed union.