Although a body of research suggests that interprofessional collaboration is hindered by the presence of professional boundaries, more recent work has demonstrated that removing these boundaries also has negative consequences for collaboration. To address these paradoxical findings, we examine two different team-level initiatives that aimed at softening and breaking down professional boundaries, drawing on data gathered from 78 in-depth interviews and two years of observations of four cross-occupational teams in the English National Health Service. Our inductive analysis of this data shows that professionals use boundaries and their manifestations —which become apparent through materialization, articulation, and embodiment— to identify and retrieve professional categories. The conspicuous presence of boundaries allows professionals to anticipate other team members’ expertise and roles, as well as different aspects of team tasks. We theorize our findings by showing how professional boundaries can be positively interlaced with interprofessional collaboration by making visible and grounding naturalized systems of classification.