With the United Kingdom’s withdrawal from the EU, in particular from its internal market, the customs union and all of the EU’s international agreements, a new chapter in Europe’s legal, economic and political history has begun. This note sets out the consequences of Brexit for investment protection and arbitration, focusing on EU-UK investment relations. In a first step, it addresses the EU-UK Trade and Cooperation Agreement’s investment protection provisions and its unique dispute settlement mechanism before turning to the fate of the United Kingdom’s bilateral investment treaties with EU Member States as well as the Energy Charter Treaty. Even though these investment treaties are likely to remain in force, the article concludes that, from the point of view of EU investors in the UK and UK investors in the EU, it can overall be seen as a clear omission that the Trade and Cooperation Agreement does not regulate investment protection in a comprehensive manner. The current situation leaves significant gaps in treaty protection, especially for investments from and into the Western EU Member States.