The present report describes four cases of brachial nerve injury caused by percutaneous radiofrequency (RF) ablation of lung cancer. All the tumors were located in the lung apex. The patients developed symptoms indicative of a low brachial plexus injury during RF ablation or as long as 7 days afterward. These symptoms partially receded over time. The indications of RF ablation in patients with apical lung cancer should be carefully determined because of the risk of brachial nerve injury associated with the procedure.