A 55-year-old female experienced acute left shoulder pain without specific trauma. Radiography showed calcific deposits in the inferior part of the glenoid fossa. Magnetic resonance arthrography showed calcific deposits in the origin of the long head of triceps brachii muscle. Conservative treatment failed to resolve the symptoms; therefore, arthroscopic surgery was performed. The patient experienced immediate and dramatic pain relief, and normal shoulder motion was demonstrated 1 year after surgery. In conclusion, although rare, calcific tendinitis of the triceps brachii muscle, which causes shoulder pain, should be included in the differential diagnosis of acute shoulder pain. Arthroscopic surgery is a treatment option for chronic cases and those resistant to conservative treatment.