Sternal dehiscence is one complication after median sternotomy. We followed a patient with sternal dehiscence for 6 months after extended thymectomy via median sternotomy. His diagnosis was myasthenia gravis without thymoma and with complicating diabetes mellitus. Sixteen days after the operation chest radiography revealed that one of six sternal wires was cut, although sternal dehiscence was not apparent. Six months after the operation, chest radiography revealed that five of six wires were cut. The patient experienced sternal dehiscence, could not cough, and felt pain at the median wound site. We implemented a resuture technique of the sternum using Shirodkar tape for postoperative sternal dehiscence. After the second operation, sternal dehiscence was not apparent. He was able to cough and had no respiratory deficiency. One year after the second operation, chest computed tomography revealed no sternal dehiscence. Shirodkar tape is extremely useful and is low in price.