Sibling relationships may be strained when one sibling is diagnosed with autism and the other is not. The way that siblings interact during play is one indicator of the quality of this relationship. Non-autistic siblings have been taught to encourage play in their autistic siblings, but there is limited literature examining the impact of intervention on the quality of the siblings' relationships. In this study, we taught four non-autistic siblings to encourage and praise play with their autistic siblings as well as self-monitor those play skills. We also measured changes in social-communicative behaviors during siblings' interactions. All non-autistic siblings learned the targeted play skills and the majority increased social-communicative behaviors. Only one autistic child increased their social-communicative behaviors toward their non-autistic sibling. On average, sibling dyads engaged in more interactions, with an increase in the duration of interactions during play. Future sibling intervention research should evaluate child characteristics and intervention factors that may influence children's response to intervention, additional interventions, and continue to incorporate other measures of relationship quality.