Anatomical variations in the formation of the median nerve are common. The third root of median nerve is of great academic and clinical significance in orthopedics, surgery, anaesthesiology, Neurophysiology, Physiatrists, Sports medicine and Physiotherapy. The aim of this study was to analyze the anatomical variations in the number of root of median nerve. A total of 14 cadavers were used for the study in the laboratory of Morphology of the University of Pamplona. It was observed that the left median nerve had three roots (one medial and two laterals).The third root originated between the origins of the lateral root and the musculocutaneous nerve from lateral cord of brachial plexus. The significance of the variations of the brachial plexus is relevant in the management of surgical exploration of the axilla and in the nerve blocks procedures of the brachial plexus.