UK government policy is encouraging healthcare staff to blur traditional roles, in the drive to increase joint working between practitioners. However there is currently a lack of clarity regarding the impact that changes to traditional working practice might have on staff delivering the services, or on patient care. In this article, we report findings from three qualitative case studies examining joint working practice in stroke care, in which the influence of professional differences was a subsidiary theme. We draw on findings from individual semi-structured interviews, as well as fieldwork observations, to describe the influence of professional knowledge and skills, role and identity, and power and status considerations in interprofessional working. The insights that were gained contribute to the understanding of how professional differences impact on healthcare staff joint working, and suggest that the elements identified need to be fully considered in drives towards changed working practice.