Collaboration with parents and caregivers to support young children's communication development is an important component to early intervention services. Coaching parents to implement communication support strategies is increasingly common in parent-implemented interventions, but few studies examine the process as well as the outcomes. We explored the triadic relationships between interventionist, parent, and child within a parent-implemented communication for toddlers with Down syndrome (DS), autism spectrum disorder (ASD), or developmental delays (DD). Time-window sequential analyses revealed that parents were more likely to use communication strategies during or immediately following coaching strategies that encouraged the parents' active role. Children were more likely to use targeted communication skills immediately following responsive parent interactions. Intervention occurred in similar frequencies across play and non-play routine contexts. This analysis provides preliminary information on understanding potential mediating variables in parent-implemented interventions. Implications for increasing parent capacity-building and child outcomes through coaching are discussed.