Objective: While the implementation of enhanced recovery after surgery protocols and improvements in pain control have decreased the length of stay (LOS) after scoliosis surgery, adolescents are typically hospitalized for several days after posterior spinal instrumented fusion (PSF). The purpose of this study was to determine whether next-day discharge after PSF for adolescent idiopathic scoliosis (AIS) had an equivalent safety profile compared with longer LOS. The secondary purpose was to examine perioperative factors associated with next-day discharge., Methods: We performed a retrospective study of all patients who underwent PSF for AIS at a single institution from 2017 to 2022. We compared patients based on postoperative LOS with an early discharge group consisting of those who were discharged on the first postoperative day 1 (POD1; n = 40) and a standard discharge group consisting of those who were discharged after POD1 (n = 71). We documented preoperative variables, including patient demographics and curve characteristics, intraoperative variables, including levels fused, implant density, operative time, and blood loss, and postoperative variables, including emergency department (ED) visits within 30 days and hospital readmissions within 90 days., Results: One hundred eleven patients were included with a mean curve magnitude of 67 degrees. Forty patients (36%) were discharged on POD1. There were one (3%) ED visit and 2 (5%) readmissions in the early discharge group and 3 (4%) ED visits and 2 (3%) readmissions in the standard discharge group (P = 0.64 and 0.55, respectively). Patients in whom intravenous methadone was used intraoperatively were more likely to discharge POD1 (P = 0.02). There were no other significant differences in perioperative variables between the two groups including: BMI, distance from home to hospital, magnitude of main curve, curve flexibility, number of levels fused, estimated blood loss, implant density, operative time, or postoperative pain scores., Conclusions: Next-day discharge after PSF for AIS has an equivalent safety profile compared with longer LOS. Over one-third of patients were discharged on POD1, and there was no statistically significant difference in ED visits or hospital readmissions between the groups. Patients in whom intravenous methadone was used intraoperatively were more likely to discharge POD1., Clinical Relevance: In a retrospective study of posterior spinal fusions for AIS, we found no increase in ED visits or hospital readmissions for those discharged the next day., Level of Evidence: Level III., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)