The focus of this article is on organisations, and the question it deals with is how the Danish Ministry of Transport has handled the requirement of integrating environmental concerns into its transport policy. Answering that question has necessitated a study focusing on organisational aspects of the ministry and its interaction with the Ministry of Environment. Neo-institutional theory is applied. Methodologically, historical analyses and case studies of concrete processes are carried through. The article concludes that several organisational barriers exist to integrating environmental concerns into transport policy. Hence, an understanding in the Ministry of Transport after which transport policy mainly deals with satisfying the demand for transport, sub-sectorizing of the ministry, and barriers found in the interplay between the Ministries of Transport and Environment. Organisational potentials are also found. The article shows that it is necessary to extend the debate about the integration principle, so that it also covers how sector ministries – which the integration principle makes into important actors – are enabled to contribute to changes in sector policies.