We evaluated fourteen patients who had restricted supination as a major impairment related with a malunited radius fracture. All patients underwent an opening wedge corrective osteotomy, bone grafting, and volar plate fixation. Clinical results were assessed based on range of motion, visual analogue scale for pain, grip power, and a Modified Mayo Wrist Score. The mean supination increased from 24 degrees preoperatively to 71 degrees postoperatively (p < 0.01). Dorsiflexion range, grip power and pain score improved significantly after the operation. The mean value for the Modified Mayo Wrist score improved from 58.6 points to 83.9 points (p < 0.01). Radiological measurements showed that the degree of dorsal angulation decreased from a mean of 9.0 degrees to -2.5 degrees after the corrective osteotomy. This study demonstrated that a malunited radius fracture with dorsal angulation, even if the latter appears mild, can induce functional impairment due to limited range of supination. Supination can be restored by an appropriately performed corrective osteotomy.