This paper examines whether reforms to the machinery of government under new labour can help to explain immigration policy change. Taking a new institutionalist approach, the paper argues that immigration policy change was partly shaped by processes of departmentalism, the joined-up government strategy and the consequential introduction of new policy actors into what had hitherto been a more tightly-knit policy network. The paper further argues that because the policymaking process has long been organised around the Whitehall model, departments have an organisational culture which shapes and structures the way policymakers perceive and frame a policy issue. When, however, actors move between departments - as a consequence of joined-up government - they apply knowledge and culture acquired from their previous department and transfer them to new policy areas. It is also the case that as a result of joined-up government, multiple departments have begun to make claims on immigration policy, with their institutionalised organisational culture and knowledge reflected in policy.