This article describes the case of a 77-year-old man with a recurrent posterior shoulder dislocation, treated with humeral hemiarthroplasty and reconstruction of a large posteroinferior glenoid defect with a bone block created from humeral head autograft. On examination, the patient's left arm was held in internal rotation against his stomach, with minimal swelling about the deltoid. His shoulder was nontender to palpation; however, he had substantial motion restrictions, and attempted motion was painful. He could forward elevate to 30°, extend to 0°, internally rotate to belly, and passive external rotation was limited to -30°. He maintained full elbow, wrist, and hand range of motion, and his neurovascular examination was intact. Radiographs revealed a recurrent posterior glenohumeral dislocation, with a large reverse Hill-Sachs defect involving the lesser turberosity and humeral head. Computed tomography with 3-D reconstruction revealed the humeral head defect involving the lesser tuberosity and approximately 40% of the humeral head and a large comminuted posteroinferior glenoid fracture measuring 2.7×0.8 cm, encompassing approximately 30% of the posteroinferior glenoid surface. Standard fixation was not possible; therefore, the resected humeral head was fashioned into an elliptical piece mirroring the size of the defect of the posteroinferior glenoid. Rough measurements of the defect were made and marked on the humeral head, which was then cut with an oscillating saw to approximate the size and shape of the defect. The glenoid graft provided an extension to the glenoid and prevented posterior subluxation with no block to motion. One year postoperatively, he had full strength (5/5) with external rotation, forward elevation, and internal rotation, 140° of active forward elevation, 30° of external rotation, internal rotation to T7, and no episodes of instability. To our knowledge. this is the first report of this technique in the literature. It is an alternative to total shoulder arthroplasty.