The transdisciplinary key worker model requires early childhood intervention professionals to make radical adjustment in their respective scopes of knowledge and practice. Focused on the author's brief experience in a key worker role, the article highlights challenges and contradictions that arise when health and welfare professionals are expected not only to exchange knowledge, skills, and expertise, but also to perform each other's work. Two contextual, reflective accounts of the reasons why social workers should be cautious in task transfers in transdisciplinary teams are given. The article renews support for social workers playing professionally appropriate roles in early childhood intervention teams in ways that can protect best service delivery to children with disability and their families.