Peer-mediated interventions (PMIs) are often used to support children with autism spectrum disorder (ASD) to develop social skills. However, more investigation is needed to better understand the role of peers as both intervention recipients and models. Sixty-five typically developing peers who participated in a PMI for children with ASD were investigated using a randomised control trial. Play sessions of the dyads were scored using the Test of Playfulness. Results showed a significant moderate intervention effect for the peers from pre- to post-intervention; outcomes for children with ASD were not influenced by peer characteristics; and, the children demonstrated a similar pattern of play interaction. Implications for practice are discussed. Clinical Trials Registry Australian New Zealand Clinical Trials Registry, https://www.anzctr.org.au/ (ACTRN12615000008527; Universal Trial Number: U1111-1165-2708).