The ulnar nerve arises as one of the terminal branches of the medial cord of the brachial plexus carrying fibers from C8 and T1, with occasional contribution from C7. There are no branches in the arm. In the forearm, it supplies the flexor carpi ulnaris and the medial half of flexor digitorum profundus. In the hand, branches include hypothenar muscles, interossei, medial two lumbricals, and adductor pollicis. Dysfunction causes ulnar claw hand, Wartenberg, and Froment signs. Entrapment of the ulnar nerve can occur at the elbow or wrist (Guyon’s canal). Treatment includes nerve decompression. Transposition can be considered in cases of revision surgery, subluxation, severe motor involvement, elbow deformity, or triceps snapping. Nerve transfer from the distal anterior interosseous nerve to the ulnar motor branch could improve outcome in cases of severe ulnar neuropathy or high ulnar nerve injury.