Launched in 1999, the European security and defence policy (ESDP)/common security and defence policy (CSDP) was not conceived as a tool to fight terrorism. This threat was traditionally considered as being of an internal nature and, thus, deemed to be addressed under the European Union's (EU) third pillar. However, the events of 11 September 2011 contributed to a shift in this approach, with several documents acknowledging the importance of the contribution of CFSP, including ESDP, in the fight against terrorism. At the rhetorical level, this idea has been consistently conveyed in the EU's framework documents and policy papers since then. Yet, both civilian and military missions undertaken in the CSDP's realm have not been systematically used to fight terrorism. Against this background, this article aims to examine the lack of impact of such missions in the framework of the Union's counter-terrorism and to discuss developments arising from the Lisbon Treaty's CSDP-related provisions. Based on an analysis of both EU missions' mandates and EU official documents, this article demonstrates that CSDP has not been used to fight terrorism nor has been transformed by the emergence of an EU counter-terrorism policy. It further puts forward three tentative causal explanations for this paradox while arguing for the existence of room for a change in this regard.