Purpose <p>This case series aims to highlight Horner’s syndrome, a clinical diagnosis of unilateral ptosis, miosis, and anhidrosis, as a rare complication of posterior spinal surgery in pediatric patients.</p> Methods <p>In this series, we present three pediatric patients who developed Horner’s syndrome after surgical correction of scoliosis involving the cervicothoracic region.</p> Results <p>Case 1 is a 12-year-old female with DiGeorge syndrome who underwent revision surgery with extension into the cervical spine after developing proximal junctional kyphosis 2&#xa0;years after her index spinal fusion procedure. Case 2 is a 9-year-old girl who had posterior spinal fusion for progressive thoracic congenital scoliosis. Case 3 is a 4-year-old female with Klippel–Feil syndrome who underwent correction of a cervicothoracic curve and hemivertebrae excision. Postoperatively, all three patients were noted to have either unilateral miosis or ptosis, with an eventual diagnosis of acquired Horner’s syndrome.</p> Conclusions <p>This case series demonstrates that Horner’s syndrome is a rare complication after a posterior spinal fusion in the pediatric population. Each case highlights that the oculosympathetic pathway can be susceptible to injury during deformity correction, specifically near the cervicothoracic region, whether from traction injury or overt nerve root transection.</p>