Calcific tendinitis of the shoulder joint, also known as chemical furuncle of the shoulder, causes intense shoulder pain and usually occurs within 1–2 cm from the insertion of the rotator cuff. We experienced a rare case of calcific tendinitis in the posterosuperior labrum of the shoulder joint in a 39-year-old male patient who presented with severe pain and weakness in the right shoulder. Radiographs and magnetic resonance imaging (MRI) findings showed calcific tendinitis in the posterosuperior labrum of the shoulder joint. A 1-week attempt at conservative treatment failed, so the calcified deposit in the posterosuperior labrum was arthroscopically removed. The patient’s symptoms were completely relieved, and satisfactory clinical outcomes were achieved. Postoperative follow-up X-ray and MRI showed no recurrence of calcific tendinitis.