Background Restoration of soft tissue balance for intraoperative posterior instability during anatomic total shoulder arthroplasty (TSA) is particularly difficult. The effectiveness of posterior capsular plication (PCP) in restoring soft tissue balance is largely unknown. The purpose of this study was to report the outcomes, complications, and reoperations of primary TSA in which a PCP was performed to correct excessive intraoperative posterior subluxation. Methods Thirty-eight shoulders (37 patients) underwent PCP for intraoperative posterior instability during anatomic TSA. The mean (standard deviation) age was 68 (10) years, and the median (range) clinical and radiographic follow-up periods were 60 (10-154) and 48 (1.5-154) months, respectively. A retrospective chart review was conducted to obtain clinical and radiographic data. Results TSA resulted in significant improvements in pain and range of motion. The mean (standard deviation) Simple Shoulder Test and American Shoulder and Elbow Surgeons scores were 9.4 (2.7) and 81.1 (19.8), respectively. PCP resulted in restoration of soft tissue balance in 27 shoulders (71%). The remaining 11 shoulders had evidence of posterior subluxation, including posterior dislocation in 2 shoulders. Revision surgery was performed in only 3 shoulders (7.9%), all for instability. However, there was a high rate of radiographic glenoid component loosening (12 shoulders, 32%). Overall results were excellent in 24 (63.2%), satisfactory in 10 (26.3%), and unsatisfactory in 4 (10.5%) shoulders. Recurrence of posterior subluxation was associated with worse motion and strength as well as with a higher rate of glenoid loosening. Conclusions PCP seems to correct excessive intraoperative posterior subluxation in approximately two-thirds of the shoulders undergoing anatomic TSA. However, posterior subluxation does recur in the remaining third, and the overall rate of radiographic glenoid loosening is of concern.