The new EU leadership has set ambitious goals for reducing global CO2 emissions through, among others, the implementation of a border carbon adjustment (BCA). The adoption of a BCA by the EU will be controversial, internally and externally, and likely to be challenged before the WTO. It is therefore key to ensure that this mechanism is structured carefully, so as to ensure its consistency with WTO rules. This article focuses specifically on the WTO provisions that would affect the design of a BCA. Although many aspects remain speculative, as existing case law provides little clarity on how WTO rules might be interpreted regarding BCAs, some general prescriptions for a WTO-compatible EU BCA can be identified. In the eventuality that the BCA would be found to be inconsistent with the EU’s substantive obligations under the GATT, exceptions are provided by the WTO which could justify any potential conflict with GATT provisions.