Posterior shoulder instability is a rare and challenging condition with a complex patho-anatomy. The role of arthroscopic repair in the treatment remains poorly defined. The purpose of this study is to evaluate the result of arthroscopic stabilization procedures in patients with posterior shoulder instability. In this case series, we treated eighteen patients (19 shoulders) with posterior shoulder instability with either arthroscopic thermal capsular shrinkage (9 patients), capsulorrhaphy (3) or labral refixation (7). There were eight male and ten female patients with a mean age of 26 years. The study group included unidirectional (6 patients; PI), bi-directional (8; PII) and multidirectional posterior instability (5; MDI). The Rowe-score and DASH-score as well as subjective and objective evaluations of the patients function, range of motion, pain and instability were used as clinical outcome measurements. At a mean follow-up of 50 months, the Rowe-score improved significantly from 46 to 74 (P = 0.005). Four patients (21%) had recurrent instability after arthroscopic treatment (2 with generalized ligamentous laxity; 3 after thermal shrinkage). Analysis of postoperative DASH-scores showed a tendency toward inferior outcomes after thermal shrinkage and in patients with an a-traumatic origin of shoulder instability. We conclude that arthroscopic shoulder stabilization by either labral refixation or capsulorrhaphy is a safe and effective treatment for posterior shoulder instability. Thermal capsular shrinkage however showed poor results and should be abandoned for this indication.