The functional recovery of hand prehension after complete brachial plexus avulsion injury (BPAI) remains an unsolved problem. The authors conducted a prospective study to elucidate a new method of resolving this injury. Three patients with BPAI underwent a new procedure during which the full-length phrenic nerve was transferred to the medial root of the median nerve via endoscopic thoracic surgery support. All 3 patients were followed up for a postoperative period of > 3 years. The power of the palmaris longus, flexor pollicis longus, and the flexor digitorum muscles of all 4 fingers reached Grade 3-4/5, and no symptoms of respiratory insufficiency occurred. Neurotization of the phrenic nerve to the medial root of the median nerve via endoscopic thoracic surgery is a feasible means of early hand prehension recovery after complete BPAI.