Children with Prader-Willi syndrome (PWS) are at risk for autism spectrum disorder (ASD), including pervasive social deficits. While play impairments in ASD are well documented, play abilities in PWS have not been evaluated. Fourteen children with PWS and ten children with ASD were administered the Autism Diagnostic Observation Schedule (ADOS) (Lord et al. in Autism Diagnostic Observation Schedule manual. Western Psychological Services, Los Angeles, 2006) as part of a larger project. A modified Affect in Play Scale (APS; Russ in Play in child development and psychotherapy: toward empirically supported practice. Lawrence Erlbaum Associates Publishers, Mahwah, 2004; Pretend play in childhood: foundation of adult creativity. APA Books, Washington, 2014) was used to score ADOS play activities. Results indicate both groups scored below normative data on measures of imagination, organization, and affective expression during individual play. In addition, the inclusion of a play partner in both groups increased all scaled scores on the APS. These findings suggest children with PWS show impaired pretend play abilities similar to ASD. Further research is warranted and should focus on constructing and validating programs aimed at improving symbolic and functional play abilities within these populations.