Abstract The purpose of this study was to evaluate the shoulder functional and radiographic outcomes of the triangle tilt surgery for treatment of shoulder deformities secondary to obstetric brachial plexus injury (OBPI). Patients and Methods: A prospective study was executed at our institution, between Dec. 2013 and Jan. 2017, on the triangle tilt procedure for treatment of 22 OBPI patients (who were available for final follow-up), with persistent medial rotation contracture, SHEAR scapular deformity and glenohumeral joint instability. Their mean age at the time of the surgery was 6.1 ± 2.2 years (range: 4 – 12 years). We excluded cases having previous tendon transfers or bony operation. Results: The mean follow-up period was 17 ± 2.2 months (range: 12 - 24 months). Clinicaly, significant improvements were noted in the mean overall Mallet score (from 11.3±1.6 to 16.9±1.8 points), also, in (external rotation, hand-to-mouth, hand-to-neck, and hand-to-spine) functions and in the posture of the arm at rest, but with no considerable improvement in global abduction. Radiographically, significant improvements were demonstrated in: posterior subluxation (from a mean of 12±7.2% to 30±3.5%), glenoid version (from a mean of −30±5˚ to −17.5±6˚) and scapular elevation (from a mean of 7.1±2 % to 2.8±0.2 %). No significant postoperative complications were noted. Conclusions: The triangle tilt procedure is an effective procedure in treating OBPI patients with secondary shoulder deformities; achieving encouraging functional and anatomical results. Keywords: Brachial plexus, SHEAR, medial rotation contracture (MRC), acromioclavicular triangle (ACT)