The purpose of this article is to describe the indications, anatomy, and harvesting technique of vascularized ulnar nerve graft based on the superior ulnar collateral artery (SUCA) for reconstruction of upper extremity function. The ulnar nerve has an extrinsic blood supply consisting of multiple dominant systems: the SUCA, the inferior ulnar collateral artery, the posterior ulnar recurrent artery, and the ulnar artery. The entire length of the ulnar nerve can survive based on the SUCA and its venae comitantes. The vascularized ulnar nerve graft is used when there is a hopeless prognosis for ulnar nerve repair. This technique may be selected if there is a definite evidence of preganglionic injuries of the C8 and T1 roots in brachial plexus injuries. This technique can be recommended for reconstruction of a large defect of the median or radial nerves in selected cases, such as upper arm replantation.