Understanding brachial plexus injury and its surgical treatment represents a challenge for medical personnel for it requires an adequate interpretation of the anatomy, histology, and pathophysiology of the peripheral nerve and its respective repair mechanisms. Neurotization is a biological phenomenon, where axonal extensions colonize the injured peripheral nerve to sustain the cell's function. This event is favored in certain surgical techniques, such as primary neurorrhaphy, nerve grafts and nerve transfers. These techniques are most widely used today for brachial plexus and peripheral nerve injuries, and if performed correctly taking into consideration a broad knowledge of the morphology of compromised tissues, they provide an opportunity for motor and/or sensory recovery with excellent functional results. The following article presents the anatomy of the brachial plexus, peripheral nerve and the physiological bases of nerve repair process to understand the principles of neurotization, and its surgical interventions in brachial plexus injury.