This paper explores the role of boundaries in a co-design process and how design work can be organized in order to manage the existing boundaries. The source of boundaries in design lies in the interface and dynamics between use practices, design practices and work practices.We will benefit from the boundary literature in order to contribute to practice-based design approaches in general, and to co-design approaches in particular.The researchis based on empirical data from a 2-year co-design process within the home care sector; involving participants from several professional groups: caregivers and care recipients. This paper focuses primarily on the caregivers (practitioners), the care recipients (elderly) and the designers. We particularly take into account the diversity of the participants in the co-design initiative and how these participants (representing two user groups) influenced the design process over time, and how their participation enabled the crossing of boundaries and the creation of a new boundary practice. Finally, the role of the designer is discussed in terms of redirecting its function towards facilitation instead of negotiation.