The UK’s decision to leave the European Union (EU) has presented innumerable challenges for both the leaving state and the EU. In these unchartered waters, the future of UK involvement in EU policies is very much in doubt. The Common Foreign and Security Policy (CFSP) has not been at the forefront of the debates about Brexit, despite the increasing focus on the EU’s global role, and the UK’s own vision of a ‘Global Britain’. The purpose of this article is to consider the past, present, and future role played by the UK in the CFSP since its inception in the Treaty on European Union. This necessitates consideration of how the CFSP might develop in the future and fulfil the goals of the recent Global Strategy. The article explores the UK’s constant opposition to greater integration in EU foreign policy and how it has purported to distance itself from the CFSP machinery. This can be contrasted with the UK’s apparent post-referendum enthusiasm for pursuing shared foreign policy goals. The future direction of the CFSP may not be affected to a significant degree by the UK’s departure. However, the CFSP will not necessarily become more integrated after Brexit. To achieve this, greater commitment will need to be shown by the EU27 to the aims of the CFSP, and other Member States will no longer be able to count on the UK as the lead voice of opposition or ‘brake’ on integration. If there is a continued desire for the UK to be involved in the CFSP, finding an acceptable model for cooperation is likely to prove a substantial, long-term challenge.