Introduction: Children with autism spectrum disorder (ASD) have difficulties with play, social interaction with peers and generalisation of intervention outcomes. The Ultimate Guide to Play, Language and Friendship (PLF) has demonstrated effectiveness in improving play performance of children with ASD and their typically developing (TD) peers. The aim of this investigation was to examine the changes in play performance when an additional TD child is added to an existing dyad of a child with ASD and a TD playmate to inform future delivery and adaptations of the intervention. Methods: Participants in this multiple case study design were five children with ASD and their TD peer who completed a dyad intervention as part of a randomised control trial investigation of the PLF and an additional TD peer who joined the play dyad. A trained occupational therapist delivered an adapted version of the PLF to the triad over four clinic sessions. An independent rater scored each child (N = 15) on The Test of Playfulness at pre- and post-triad intervention. Line graphs were used to examine case data and compare to dyad play performance and patterns of interaction. Results: Four of the five children with ASD generalised their play performance from the dyad to the triad social environment. However, the triad intervention did not demonstrate improvements in play performance. The play performance scores for the children with ASD and their TD peers were variable and demonstrated changes in their play pattern from the dyad to the triad. Conclusion: This investigation delivered preliminary evidence of play performance generalisation from a dyad to a triad with TD peers for children with ASD. Careful consideration of characteristics of all playmates is recommended for delivering the intervention to support play performance of children with ASD.