Patients with adolescent idiopathic scoliosis (AIS) are typically treated surgically with posterior spinal fusion (PSF) when the curve continues to progress beyond 45 to 50 degrees. In adult patients, studies have shown that preoperative psychiatric diagnoses are associated with poorer clinical outcomes after lumbar spine surgery. This study aims to address whether a preoperative mental health disorder affects outcomes in pediatric patients with AIS treated with PSF. We conducted a retrospective study of pediatric patients with a history of AIS requiring operative treatment with PSF at a single center with a minimum of 2-year follow-up. These patients were split into 2 groups: a subset that had a mental health disorder (MHD), and a control group. The MHD subset included patients with anxiety disorder, major depressive disorder, bipolar disorder, manic disorder, obsessive-compulsive disorder, attention deficit hyperactivity disorder, and stress disorder. The 2 groups were compared using independent student t-test and χ2 analysis. A total of 417 patients were included in the study. Ninety-three patients were included in the MHD group, and 324 patients were included in the control group. The mean pain score for the MHD group was greater (3.93) compared with the control group (3.34). The PCA demands during inpatient stay for the MHD group were also greater (236.7) compared with the control group (140.0). There was no significant difference in the length of stay in the hospital between the MHD group (4.7 days) and the control group (4.6 days). There was a greater number of patients in the MHD cohort (25.8%) still using narcotic pain medication at first follow-up compared with the control group (12.0%). This study suggests that patients with AIS with a preoperative mental health disorder undergoing PSF experience more pain after surgery and require more pain medication during their recovery. III. This is a retrospective review of pediatric patients with adolescent idiopathic scoliosis and a preoperative mental health diagnosis and their pain management requirements during the recovery period from posterior spinal fusion.