Traumatic brachial plexus injury is the most common indication for functional free muscle transfer, and elbow flexion recovery is the functional target, followed by shoulder stability and hand reanimation. In this article, we provide a literature review of functional free muscle transfer (FFMT) for adult traumatic brachial plexus injuries and the surgical technical recommendations to achieve the best functional results with FFMT for adult traumatic brachial plexus injuries.