Brachial plexus injury is a rare complication after median sternotomy. We investigated that injury to the brachial plexus was retrospectively assessed in the results of three patients who underwent median sternotomy for open heart surgery.All patients were placed in the hands-up position after right internal jugular vein cannulation, and the internal mammary artery was prepared for all of those. Nerve conduction measurements and electromyography were performed besides neurological examination.Brachial plexus injury was detected in three cases (0.5%) of 575 patients who underwent coronary artery bypass grafting with median sternotomy. The main symptoms were continuous pain, and motor and sensory disturbances at the affected upper extremity (left arm in all cases). The common feature was that in all cases the left internal mammary artery was harvested. While the symptoms were relieved in two patients about six months after the operation, the other one had intractable pain and paresthesia.The most important measure is careful sternal retraction and use of the hands-up position for the low incidence and benign course of brachial plexus problems. Inappropriate sternal retraction during preparation of internal mammary artery should be avoided.