Purpose <p>Posterior shoulder instability, often related to glenoid dysplasia, can also be associated with inferior capsuloligamentous instability. This study presents the technical procedure of the retroglenoid osteotomy with posterior capsular shift, supported by clinical and radiological evaluation. Our hypothesis was that the re-orientation of the glenoid and the capsular retensioning could achieve shoulder stability.</p> Methods <p>Eleven shoulders of nine patients with posterior shoulder instability and glenoid dysplasia underwent retroglenoid osteotomy with posterior capsular shift. A graft was inserted into the posterior opening, with full respect of the anterior wall of the scapular neck. The technique is detailed. Clinical, radiological, and functional outcomes were assessed over an average follow-up period of 20 months.</p> Results <p>This study showed clinical improvements in all patients, with the complete resolution of instability symptoms and radiological correction of glenoid retroversion. No complications or re-operations were observed. Range of motion in the shoulder joints was preserved, and patients reported satisfaction with their outcomes. The total Constant Score increased from 58.2 to 76 points, the mean post-operative Walch-Duplay score was to 92 points (10–100).</p> Conclusion <p>In the context of posterior shoulder instability with glenoid dysplasia and inferior laxity, the retroglenoid osteotomy associated with the posterior capsular shift offers substantial clinical improvement in the short term, leading to symptoms resolution, stable shoulder and radiological correction of glenoid retroversion.</p> Level of evidence <p>level 4 Current clinical practice.</p>