BACKGROUND CONTEXT: Revision risk after pediatric spine surgery is not well established and varies between deformity etiologies. PURPOSE: To report the 2-year revision risk following surgery for primary pediatric spinal deformity in a nationwide cohort and to evaluate potential risk factors and reasons for revision surgery. DESIGN: Retrospective nationwide cohort study. PATIENT SAMPLE: A national registry study of all pediatric spinal deformity patients undergoing surgery during 2006–2015 (n=1310). OUTCOME MEASURES: Two-year revision risk. METHODS: All patients ≤21 years of age undergoing spinal deformity surgery in Denmark during 2006–2015 were identified by procedure and diagnosis codes in the Danish National Patient Registry (DNPR). Data on revision surgery were retrieved from the DNPR. Patients were categorized in six groups according to etiology. Medical records were reviewed for reason for revision in all patients. Potential risk factors for revision were assessed with multiple logistic regression analyses and included age, etiology, sex, Charlson comorbidity index (CCI), and growth-preserving treatment. RESULTS: Patients were categorized according to etiology: idiopathic deformity (53%), neuromuscular deformity (23%), congenital/structural deformity (9%), spondylolisthesis (7%), Scheuermann's kyphosis (5%), and syndromic deformity (3%). Of 1,310 included patients, 9.2% underwent revision surgery within 2 years and 1.5% was revised more than once. Median time to revision was 203 (interquartile range 35–485) days. The multivariable logistic regression found significantly higher odds ratio (OR) for revision in patients with growth-preserving treatment (OR=5.1, 95% confidence interval [CI] 2.6–10.1), congenital deformity (OR=2.7, 95% CI 1.3–5.3), spondylolisthesis (OR=3.5, 95% CI 1.9–6.7), Scheuermann kyphosis (OR=3.9, 95% CI 1.9–8.3), and CCI score ≥3 (OR=2.5 95% CI 1.1–5.6). The most common reason for revision was implant failure (32.5%) followed by residual deformity and/or curve progression (15.8%). CONCLUSIONS: In this nationwide study, the 2-year revision risk after primary pediatric spinal deformity surgery is 9.2%. Risk factors for revision are etiology of congenital deformity, spondylolisthesis, Scheuermann kyphosis as well as patients with growth-preserving treatment and higher CCI. The most common reason for revision is implant failure.