BACKGROUND: Prader-Willi syndrome (PWS) is a rare disease. Hip dysplasia is an orthopedic-related disease of PWS. Limited literature exists on the prevalence, diagnosis, and surgical management of late diagnosed hip dysplasia in PWS. This study assessed the prevalence of hip dysplasia in children with PWS and evaluated the outcomes following surgical intervention of late diagnosed hip dysplasia. METHODS: A retrospective analysis was conducted on patients diagnosed with PWS at our institution from January 1, 2017 to December 31, 2021. Patient demographics were collected, the acetabular index (AI) and the central edge angle (CEA) were measured. A single fellowship-trained pediatric orthopedic surgeon determined the presence of hip dysplasia based on radiographic measurements. RESULTS: The prevalence of hip dysplasia with PWS is 33.3%. There was no significant association between prevalence and sex or genetic subtype. The mean age at the time of diagnosis was 34.4 months (6 months to 109 months). Five patients (2 right side, 3 bilateral) underwent surgical intervention at an average age of 82.4 months. The acetabular index decreased from 42.8 ± 5.9 degrees preoperatively to 21.7 ± 7.7 degrees postoperatively. No serious postoperative complications were reported during the follow-up. CONCLUSIONS: The present study demonstrated a higher prevalence of hip dysplasia in patients with PWS than in the general population. The prevalence does not significantly differ across sexes or genetic subtypes. While preliminary findings suggest outcomes may be comparable to those of HD without PWS, further studies with larger cohorts are required to validate these observations.