Children with Prader-Willi syndrome (PWS) and autism spectrum disorder (ASD) present with challenges in social cognitive ability, Research comparing PWS to ASD is important given the implication of 15q11-q13 region in the biology of autism. However, recent findings question the accuracy of relying solely on parent report in behavioral characterization. Thus, this study examined social cognition in an observable pretend play task and by parent report in 50 preschool children (ages 3-5) with PWS, by subtype, compared to ASD. Behaviorally, the paternal deletion subtype expressed overall higher functioning, whereas the maternal uniparental disomy subtype performed more similarly to the ASD group. Results are the first to show deficits in social cognitive ability early in development. The severity and differences in deficits between PWS subtypes are important in informing early intervention efforts.