Purpose <p>Spinopelvic fusion with sacral-alar-iliac (S2AI) screws effectively corrects spinal and pelvic deformities in neuromuscular scoliosis (NMS). However, postoperative hip pain may compromise functional outcomes. This study investigates the incidence and risk factors for hip pain after spinopelvic fusion in pediatric NMS patients.</p> Methods <p>We retrospectively reviewed 73 nonambulatory pediatric NMS patients who underwent spinopelvic fusion with S2AI screws from 2013 to 2022. Patient records were analyzed for hip symptoms, demographics, and radiographic parameters using logistic regression, ROC curve, and Kaplan-Meier survival analyses.</p> Results <p>Twenty-one patients (29%) experienced postoperative hip pain, with 71% occurring within the first year. Six patients needed additional hip surgery. Logistic regression revealed postoperative pelvic obliquity (PO) (OR: 1.165, <i>p</i> = 0.009) and sacral slope (SS) (OR: 1.055, <i>p</i> = 0.023) as significant predictors. Clinical thresholds of postoperative PO ≥ 7° (OR: 5.275, <i>p</i> = 0.01) and SS ≥ 38° (OR: 8.051, <i>p</i> = 0.002) were independent risk factors. The hip pain group showed significantly higher rates of femoral head deformity (57% vs. 17%, <i>p</i> = 0.001) and hip osteoarthritis (24% vs. 6%, <i>p</i> = 0.039). Kaplan-Meier analysis revealed shorter hip pain-free survival in patients with postoperative PO ≥ 7° (<i>p</i> = 0.002) and SS ≥ 38° (<i>p</i> &lt; 0.001).</p> Conclusions <p>Hip pain affects nearly one-third of NMS patients after spinopelvic fusion, primarily within the first postoperative year. Postoperative PO ≥ 7° and SS ≥ 38° significantly predict hip pain development. Close monitoring during the early postoperative period and alignment optimization may help prevent this common complication.</p> Level of evidence <p>Prognostic Studies, Level III.</p>