This paper seeks to document the impact of structural and organisational change brought about through devolution on the UK's handling of European policy, and thereby to illustrate the nature of the new multi-level governance in the devolving UK. In the context of arrangements prior to devolution, we examine distinctive features of the new constitutional and structural framework of EU policy-making; the guidelines and conventions for the multi-levelled management of policy in this area; and the impact of central versus territorial political and cultural features. Employing an historical-institutionalist approach and drawing on a series of elite interviews conducted in London, Edinburgh, Cardiff and Brussels, we consider the impact of distinctive features of the devolution arrangements on European policy making. These include the ad hoc nature of the devolution process; 'constitutional asymmetry'; and problems of 'policy overlap' and 'policy contagion'. We find that the ongoing process of devolution is increasing the administrative and political complexity of European policy making in ways which potentially challenge the customary UK policy co-ordination and coherence in such matters. Whereas during the initial 'constitutive' phase of the devolution process continuity of past administrative practice has prevailed, the devolved authorities in Scotland and Wales have the potential to introduce a stronger territorial input into European policy making.