Objectives <p>Children with Prader-Willi Syndrome (PWS) struggle with social cognition, emotional expression, and related pretend play skills. Pretend play serves as a naturalistic mode of engagement through which children with PWS can build these important developmental skills. The present study expands upon a preliminary study to further examine the effectiveness of specific intervention strategies, such as prompting the child or modeling, within a pretend play intervention for school-aged children with PWS (<i>n</i> = 28).</p> Methods <p>Behaviors were coded during four intervention sessions per participant. ANOVAs, correlations, and hierarchical linear modeling examined moment-to-moment and long-term relationships between interventionist strategies and child play behaviors.</p> Results <p>Findings indicated that reflection/summarization and modeling most often preceded pretend play and predicted growth of these skills over time. Direct prompts/questions showed mixed effectiveness but most often preceded child expression of affect in play.</p> Conclusions <p>Strategies of modeling and reflecting/summarizing may most effectively support pretend play skill growth in children with PWS. Care must be taken to consider the utility of prompts or questions in play interactions. Overall, an intermediate level of support may most optimally engage children with PWS and can be implemented in future interventions to support pretend play and socioemotional skill growth.</p>