Posterior shoulder instability with glenoid deficiency is a rare entity and its surgical treatment is challenging. Reconstructive techniques have focused on extra-articular structural bone transfer that obstructs humeral translation and thereby prevents glenohumeral dislocation. However, long-term results are not as promising. In this report, the authors describe a technique for anatomic posterior glenoid reconstruction using an osteoarticular distal tibia allograft in two patients including their outcomes after 2 years. Level of evidence IV.