Chronic instability of the sternoclavicular (SC) joint is a challenging clinical problem, particularly in a patient population for which nonoperative forms of treatment prove ineffective. Patients present after experiencing recurrent subluxation events and subsequent pain, which commonly result in increasing functional limitation. Recurrent SC joint instability of this nature can lead to damage of the SC joint cartilage and bone, and in cases of posterior subluxation or dislocation, damage to mediastinal structures. While the precise treatment algorithm requires tailoring to individual patients and their respective pathologies, we have demonstrated successful outcomes in correcting chronic SC joint instability by means of SC joint reconstruction with semitendinosus allograft, SC joint capsular reconstruction, and, in cases of arthritic damage, resection of a small portion of the degenerative component of the medial clavicle. The purpose of this Technical Note is to describe a technique that uses a semitendinosus allograft to stabilize the SC joint combined with a capsular reconstruction in patients who have previously failed nonoperative treatment methods