We report a case of carpal tunnel syndrome caused by volar dislocation of the lunate in a patient with rheumatoid arthritis. A 74-year-old woman complained of numbness in her fingers. Carpal tunnel syndrome was diagnosed, and carpal tunnel release was performed. However, the symptoms recurred. Three-dimensional computed tomography and magnetic resonance imaging revealed volar dislocation of the lunate and synovitis around the distal radioulnar joint, respectively. Resection of the lunate and the Sauvé–Kapandji procedure were effective.