Social studies on biobanking have traditionally focused on public engagement, that is, engagement with donors, patients and the general public as an important factor of sustainability. In this article, we claim that, in order to fully understand the way biobanks work, it is necessary to pay attention to a number of other actors, which have an equal, if not greater, impact on their practices and strategies. This means taking a broadened approach to biobank engagement. By using data collected from interviews with different biobank experts based in five different countries (UK, Canada, Finland, Spain and Iceland), we identify seven communities, including the public, that emerge as relevant. Such relationships condition the way biobanks develop, act and plan. The discussion illustrates how the relationships with those seven communities are articulated. We conclude that there is a need for a broadened approach to biobank engagement in order to understand biobank sustainability.