BACKGROUND: Delayed-onset neurologic changes (DONCs) following spinal deformity surgery are poorly understood and are often devastating. METHODS: A retrospective review of cases from 12 hospitals was performed. The clinical and radiographic parameters of patients who experienced a new DONC after spinal deformity correction were evaluated. RESULTS: Eighteen patients, with a mean preoperative major Cobb angle of 75° ± 24°, were included. The mean age at surgery was 13 ± 2 years, and 6 patients (33%) were male. Seven patients had temporary intraoperative neuromonitoring changes. Fourteen patients (78%) had neurologic changes within 24 hours postoperatively (range, 3 to 24 hours). Of 16 patients with blood pressure data, 8 (50%) had at least 1 documented episode of hypotension surrounding the change in neurologic status. No misaligned implants were seen on axial imaging. Fourteen patients (78%) were treated with vasopressors. Sixteen patients (89%) returned to the operating room, and 11 patients (61%) underwent implant removal. Seven patients (39%) sustained a spinal cord infarct, with only 1 (6%) experiencing recovery beyond an ASIA (American Spinal Injury Association Impairment Scale) score of B. Ten (91%) of the 11 patients without an infarct demonstrated recovery (5 patients with an ASIA score of D and 5 with a score of E). CONCLUSIONS: A DONC is a rare complication of spinal deformity surgery. This study represents the largest documented series of DONCs and highlights the multifactorial and still poorly understood nature of this condition. The primary modifiable risk factor may be hypotension in the postoperative period: 50% of patients had a mean arterial pressure below the 5th percentile for their height, as documented around the time of the neurologic change. Eighty-six percent of patients with a spinal cord infarct had minimal neurologic recovery, whereas nearly all of the patients without an infarct did recover function. The management of this condition may include elevation of blood pressure with temporary implant removal. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.