Restoration of digital flexion after brachial plexus injury or forearm injury has been a great challenge for hand surgeons. Nerve transfer and forearm donor muscle transfer surgeries are not always feasible. The present study aimed at evaluating the effectiveness of restoring digital flexion by brachialis muscle transfer. Ten lower brachial plexus- or forearm-injured patients were enrolled. After at least 12 months following surgery, the middle-finger-to-palm distance was less than 2.5cm in six patients. In the other four patients with less satisfactory results, secondary tenolysis surgery was performed and the middle-finger-to-palm distances were reduced to 2.0-4.0cm. The average grasp strength was 204kg. Elbow flexion was not adversely affected. In conclusion, brachialis muscle transfer is an effective method for reconstructing digital flexion, not only in lower brachial plexus injury, but also in forearm injury patients. Level of evidence: IV