Current government policy aims to create a wider ‘community of public health practice’ within local systems, working in a coherent and coordinated way in partnership with local people to reduce health inequalities. However, for this to happen policymakers and practitioners across the public sector have to reconsider boundaries, role definitions, professional identities and responsibilities. On the basis of documentary analysis and fieldwork involving interviews with individuals from various sectors and nonparticipant observation of public health nursing and primary care organizations within two local health economies in England, the paper explores the ways in which these processes of reconfiguration have been developing in local health systems. It illuminates new exclusions and tensions emerging from inherent contradictions in national policy and from difficulties individuals have thinking beyond existing spatial, conceptual and organizational boundaries and divisions. Paradoxically, therefore, rather than opening up new spaces for public health practice these tensions may ‘force’ some people back into narrower more traditional roles or ultimately out of public health altogether. The paper also uses the notion of communities of practice to explore issues of ‘agency’ in professional practice – that is the way in which individuals reflexively construct their practice and in so doing engage with or resist the relevant policy imperatives. The research illuminates some of the boundaries that are operating to discourage people from engaging with public health. This analysis suggests people may need more time and support to respond constructively to the new public health agenda. Without this, potential members of the wider public health workforce may respond defensively and resist alignment to public health goals in order to protect their embattled workspaces.