Background: Engagement of the child, parent and professional may facilitate positive outcomes for young children with communication disorders receiving early intervention (EI) via telepractice. Despite reported positive outcomes of engagement in a family-centred model of EI, there is limited research exploring the nature engagement in the telepractice environment and guiding professionals on how to best interact with young children and their families. Aim: To identify a set of critical behaviours for building engagement in telepractice EI. Methods & Procedures: A two-round modified e-Delphi study was conducted. Participants were international experts in the field of paediatric communication disorders and telepractice EI from diverse allied health and education backgrounds. The experts used a nine-point Likert scale to rate the importance of a predetermined set of critical behaviours for building engagement in telepractice EI across three different aspects of the telepractice interaction: (1) getting to know each other; (2) family-centred telepractice; and (3) telepractice specific considerations. Outcomes & Results: A total of 30 experts completed round 1, with 21 participants from round 1 completing round 2 (70% response rate). Across the two rounds, a total of 64 of the 109 items presented (58.71%) achieved consensus as critical behaviours for building engagement in telepractice EI. Conclusions & Implications: The present study identified a set of individual aspects of the telepractice interaction that participants, particularly professionals, may need to intentionally address to engage with families of young children with communication disorders receiving EI via telepractice. The results from this study will contribute to the development of an observational tool to measure engagement in the telepractice EI environment.