Introduction:Lipoma arborescens is a tumor-like lesion that occurs inside joints and synovial bursae, especially in knee joints. It rarely occurs in the shoulder joints and this disease usually causes severe shoulder pain. This study aims to report a rare case of lipoma arborescens occurring in the subdeltoid bursa with severe shoulder pain. Case Report: A 59-year-old woman with severe pain and restriction of range of motion (ROM) for her right shoulder consisting for 2 months was referred to our hospital. Magnetic resonance imaging (MRI) findings revealed that a tumor-like lesion exists in the subdeltoid bursa in her right shoulder and blood examinations revealed no abnormal findings. Surgical resection of the tumor-like lesion was performed and the rotator cuff was repaired because this tumor-like lesion invaded the rotator cuff partially. Pathology examination of the resected tissues was consistent with lipoma arborescens. One year after surgery, the patient’s shoulder pain was diminished and its ROM recovered. There was no significant difficulty in activities of daily living. Conclusion: Lipoma arborescens should be considered when patients present with complaints of severe shoulder pain. Even if their physical findings do not suggest rotator cuff injuries, MRI should be performed to rule out lipoma arborescens. Keywords: Lipoma arborescens, shoulder, subdeltoid bursa.