Children with permanent brachial plexus birth injury have a high risk of developing posterior shoulder subluxation. In 2010, we implemented a protocol to reduce the incidence of this deformity, including early passive exercises, ultrasound screening, botulinum toxin-A injections, shoulder splinting and targeted surgeries. Two-hundred and thirty-seven consecutive children treated at our institution, with a mean follow-up of 11 years (range 1 to 17) were compared in three groups: children born from 1995 to 1999 (n = 53), 2000-2009 (n = 109) and 2010-2019 (n = 75). Posterior shoulder subluxation developed in 48% of all patients but the mean age at detection of shoulder subluxation decreased from 5 years to 4.9 months. Need for shoulder relocation surgery also decreased from 28% to 7%. Mean active shoulder external rotation in adduction improved from 2° to 46°. In conclusion, our established protocol has the potential to reduce the incidence of posterior shoulder subluxation in children with brachial plexus birth injury.Level of evidence: II.