Traumatic sternoclavicular dislocation is a rare injury corresponding to less than 5% of all injuries of the scapular belt. It is preferentially treated through reduction of the sternoclavicular joint, symptom relief, a brief period of immobilization and rehabilitation, with the aim of gaining strength and range of motion. In some patients, however, this type of injury may progress with instability and pain, thus causing discomfort and pain. On such occasions, surgical treatment is chosen. The objective of this study was to report the clinical case of a sports player who progressed with chronic traumatic anterior instability of the sternoclavicular joint and underwent reconstruction using the ipsilateral semitendinosus tendon. This was a 16-year-old male patient who was a state-level judo player. Following a fall during a fight, he presented pain, slight deformity and edema in the right sternoclavicular joint, and he underwent conservative treatment for 12 months, without success. In the end, reconstruction of the sternoclavicular joint was carried out using the ipsilateral autologous semitendinosus, with resection of the intra-articular disc and suturing of the costoclavicular ligaments. We have presented a case of dislocation of the sternoclavicular joint in a high-performance judo player who underwent reconstruction using the semitendinosus, with excellent functional results after 1 year of follow-up.