Background: Peer-mediated pragmatic language interventions can be of benefit to children with autism as they simultaneously target an individual child's pragmatic language skills and contextual factors related to social interactions. However, little is known about peer outcomes following peer-mediated interventions. Aims: This study evaluated the pragmatic language outcomes for typically-developing (TD) playmates who participated in a peer-mediated intervention for children with autism. Methods: Dyads (child with autism and TD-playmate; n = 71) were randomised to a treatment-first or waitlisted-first comparison group. Dyads attended 10 clinic play-sessions with a therapist and parents mediated home-practice. The Pragmatics Observational Measure 2nd edition (POM-2), and Social Emotional Evaluation (SEE) evaluated pragmatics before, after and 3-months following the intervention. Results: Changes in both outcomes measures were equivalent for intervention-first and waitlisted TD-playmates, but all TD-playmates made significant gains in pragmatics following the intervention. Treatment effects maintained for 3-months (p < 0.001–0.014, d = 0.22–0.63), were equivalent in different environments (clinic and home). Peer relationship type and therapist profession mediated POM-2 scores across the study, while expressive language ability moderated SEE scores. Conclusions: This peer-mediated intervention had a positive impact on TD-playmate's pragmatic language capacity and performance.