The purpose of this case study was to promote the social interaction and responsiveness to peer initiations of a child with autism spectrum disorder (ASD). The study was conducted during the school recess at a Japanese elementary school. A child with ASD in a special needs education class and three peers in a general education class participated. Following a pre-assessment, we contrived joint playtime for the child with ASD and her peers. We then introduced a social skills training component at the beginning of each playtime for both the child with ASD and her peers. During the pre-assessment, no social interaction was observed for the child with ASD. After contriving the joint playtime, the social interaction between the child with ASD and the peers was observed. Conducting the social skills training further increased the social interaction and improved the responsiveness to peer initiations. To evaluate generality of the intervention effects, we observed the social interaction of the child with ASD when she participated in the inclusive general education class. We also observed her on-task behavior in the general education class to see whether her performance in the class improved after the intervention. Both her social interaction and her on-task behavior increased after the intervention. Implications for future study are discussed.