The ulnar intrinsic muscles contribute to pinch, grip strength, and hand dexterity. Following severe compression or traumatic proximal injury to the ulnar nerve, distance and subsequent time to recovery limit options for recovering intrinsic function. The AIN-to-ulnar nerve (pronator quadratus branch of the anterior interosseous nerve to the motor fascicles of the ulnar nerve) transfer has the potential to restore ulnar lumbrical and interossei muscle function by moving the nerve reconstruction closer to the target muscles. Postoperative therapy includes three phases based on the donor activation focused rehabilitation approach. Therapy progresses based on results of monthly manual muscle testing of the recipient ulnar intrinsic muscles. Frequent donor activation with active forearm pronation is encouraged throughout the first two phases. Exercise and functional activities that combine donor pronation with assisted and active recipient function are included in the motor reeducation. An anti-claw orthosis is advocated until clawing is resolved.