Lipoma arborescens is a rare intra-articular lesion consisting of villous lipomatous proliferation of the synovium that tends to occur in the knee joint, especially in the suprapatellar pouch. The lesion has been observed in other locations, including the glenohumeral joint, subdeltoid bursa, hip, and elbow. We report a case of a lipoma arborescens of a unilateral hip joint in a 34-year-old man. MRI and a whole body bone scan were performed. In addition, a surgical synovectomy was performed and microscopic examination of the tumor revealed multiple variable-sized villous masses composed of mature fat tissue and lined by synovial cells which confirmed the diagnosis of lipoma arborescens.