The medial pectoral nerve (MPN) is the most commonly reported collateral branch of the brachial plexus (BP) used as an infraclavicular intraplexal donor to reinnervate the musculocutaneous nerve (MCN) and restore elbow flexion after partial BP injuries. Alongside the thoracodorsal nerve (TDN), the most commonly reported alternative donor, the MPN transfer offers several advantages over classical intraplexal and extraplexal options. While the TDN is less often viable in partial BP injuries and thus less frequently reported, MPN use may be limited by a higher rate of diameter mismatch and often insufficient length for a direct, tension‑free coaptation with the MCN. Therefore, selection of the MPN should be based on meticulous intraoperative assessment. This chapter outlines the general principles of infraclavicular intraplexal nerve transfers, details the anatomical and technical foundations of MPN-to-MCN transfer, and discusses controversies, challenges, and potential solutions drawn from published evidence and personal experience.