Individuals with Prader-Willi Syndrome (PWS) are at risk for autism spectrum disorder (ASD), including socialization problems. The PWS chromosome 15q11-13 maternal uniparental disomy (mUPD) subtype displays greater ASD symptoms than the paternal deletion (DEL) subtype. Since interpreting faces leads to successful socialization, we compared face discrimination in PWS with ASD to explore the socialization characteristics of these disorders. Although face processing impairment in ASD is well documented, PWS face processing research is limited. Forty-four PWS participants (14 DEL and 19 mUPD) and 17 participants with ASD were measured on face discrimination. PWS and ASD participants scored in the impaired functioning range. For primary findings, DEL and mUPD PWS genetic subtype groups did not differ. These findings suggest PWS individuals, regardless of subtype, show impaired face processing similar to ASD. This research highlights the need for additional research on social cognitive functioning in PWS to understand the role of 15q11-13 in ASD.