Objective To evaluate the effect of high-dose prednisolone on the functional outcome of patients with early-stage primary frozen shoulder. Methods Eighteen patients treated with oral prednisolone at an initial dose of 1 mg/kg/day for primary frozen shoulder were retrospectively evaluated. The patients' range of motion, Disabilities of the Arm, Shoulder, and Hand (DASH) score, Constant-Murley score, American Shoulder and Elbow Surgeons (ASES) score, and visual analog scale score were recorded at baseline and at 4 weeks and 6 months after treatment. Results Rapid recovery of shoulder motion was noted at 4 weeks with the exception of abduction, which was maintained at 6 months. Significant improvement in pain perception and the Constant-Murley score was evident at 4 weeks and extended to 6 months. The DASH and ASES scores did not show significant improvement in the first 4 weeks but were significantly improved at 6 months. Conclusion High-dose oral prednisolone treatment provides rapid symptom resolution that persists long after drug discontinuation. The early treatment period is characterized by marked reduction in pain and rapid recovery of shoulder motion. Improvements in functional outcomes and disability indices tend to be more subtle in the early period but significantly improve during late treatment.