Background: The feasibility of using typically developing siblings as social interaction intervention agents has been suggested in the literature addressing interactions and relationships between children with disabilities and their siblings. However, the outcomes are not completely understood. Objective: This study evaluated an intervention that targeted the social play of children with developmental disabilities (DD) that was implemented by typically developing brothers in the children's home settings. Method: A multiple-baseline design across three sibling dyads was used to examine the effectiveness of the social interaction intervention. Results: The findings resulted in a moderate change in social behaviors of children with DD and increased social skill strategies used by typically developing boy siblings. Percentage of non-overlapping data and Tau-U indices were provided and discussed for the use of sibling-mediated social play intervention with children with DD. Conclusion: The goal of sibling-mediated social interaction intervention is to provide typically developing siblings with specific techniques to engage children with disabilities in play, with the intention of encouraging their active participation to improve the quality of their interaction. By individually fine-tuning the activities to meet the interests of both children with disabilities and their siblings, typically developing siblings can be taught some social competencies that have value not only for children with disabilities, but also for themselves. They can become cognitively aware of their own thought processes.