It is no secret that while the European Union (EU) has taken up commitments to combat climate change under the United Nations Framework Convention on Climate Change Paris Agreement and its own 2020 and 2030 climate and energy package strategy, the Union continues to be heavily dependent on the import of fossil fuels from abroad. One may even say that this leads to a cognitive dissonance, i.e. the discomfort which ensues if one holds two contradictory values, with respect to the externalisation of the Union’s energy and sustainable development policy. On the one hand, the EU aims to become a global frontrunner in the field of promoting renewable energy and sustainable development. This expresses itself through the inclusion of specific chapters on Trade and Sustainable Development in the EU’s Free Trade Agreements (FTAs) (standard since the 2011 EU-South Korea FTA). On the other, the EU realises that it is imperative to secure the Union’s security of energy supply, still largely guaranteed by fossil fuels. Therefore, the Union in parallel attempts to eliminate discriminatory practices in international fossil fuel trade in its bilateral agreements (e.g. in the EU-Ukraine Deep and Comprehensive Free Trade Agreement). This paper will explore the root causes of this cognitive dissonance and research what elements could contribute to ensuring more coherence in EU external energy policy. The objectives of sustainable development and security of supply are not necessarily contradictory per se. However, clearer delineations between the two objectives are necessary in EU external relations in general, and in the Union’s FTAs more specifically. This also applies to relations between Member States and the Union in this area, as well as to the interactions between the relevant EU institutions tasked with energy, sustainable development and the environment.