This study evaluated the effects of using preferred activities with peer support on the social interactions of preschoolers with autism spectrum disorder (ASD) and their typically developing peers. Two preschool-age children with ASD and six peers in an inclusive classroom participated in this study. A multiple-probe single case experimental design across three peers was employed. Results indicated that the participants' social initiations and responses, as well as the percentage of time engaged in social play, increased following the preferred activity. Gains were also demonstrated across social interactions and time engaged in the preferred activity plus peer support condition. Increases in social interaction behaviors in typically developing peers were also observed, and positive intervention gains were maintained during 5-week follow-up sessions. Implications for research and practice for improving interaction between children with and without ASD in inclusive preschool settings are discussed.