Elbow flexion is vital to arm function. Following a five-root-level brachial plexus injury, a nerve transfer using extraplexal nerve donors is needed to restore elbow function. The intercostal nerve (ICN)-to-musculocutaneous nerve transfer is a viable surgical option. Rehabilitation following this transfer involves the three-phase DAFRA guidelines (donor activation focused rehabilitation approach), in which exercises progress based on manual muscle testing (MMT). The hallmarks of phase one include patient education and donor activation. Intercostal muscle actions include trunk flexion/rotation and inspiration/expiration and are performed frequently throughout phases 1 and 2. Cortical plasticity is enhanced by co-contracting the donor muscles with passive elbow flexion. Following the first sign of biceps muscle recovery, the second phase of rehabilitation begins. During this phase, donor activation exercises (trunk flexion) are paired with simultaneous active-assisted elbow flexion, starting in a gravity-assisted plane. Exercises are gradually progressed to gravity-eliminated and then against gravity. The third and final phase of rehabilitation focuses on strengthening with resistance and, when possible, on independent recipient contraction of the biceps without donor activation. It may take several years before the patient reaches this stage, and not all patients will achieve more than 3/5 MMT strength.