Background: In total brachial plexus injury, intercostal nerves (ICNs) are used as donor nerves to restore the elbow flexion; albeit in upper brachial plexus injury (BPI), ulnar nerve provides a source of motor axons for this purpose. The present study set out to compare the restoration of elbow flexion by using these two donor nerves. Methods: Between 2010 and 2013, 24 adult patients with upper-middle BPI and 15 patients with total BPI undergoing elbow flexion restoration surgery were studied. Motor fascicle of flexor carpi ulnaris branch of ulnar nerve (mFCU nerve) procedure was utilized in upper-middle BPI, as well as transfer of ICN to biceps branch of the musculocutaneous nerve (MCN) in total BPI. Both techniques included sectioning, rerouting, and direct suturing of the biceps branch of the MCN. Follow-up consisted serial clinical examinations and EMG–NCV tests. Motor strength was recorded according to the British Medical Research Council grading system in that the results were reported as nonfunctional (grades M0–M2) and functional (grades M3–M5). Result: No significant difference was documented between the Oberlin procedure and ICN–MCN transfer in terms of reinnervation results (P = 0.6). However, a significant difference in restoration of muscle force was found between the mFCU (95.83%) and ICN–MCN transfers (66.66%) (P = 0.02). Conclusion: The evidence from the present study indicates that although ICN–MCN transfer is a viable method for reanimation of elbow flexion in BPI, mFCU nerve is a better donor if exists.