This article aims to analyse legitimacy of military crisis management operations carried out by the EU in support of the UN in sub-Saharan Africa by using Mark Suchman’s typology of organizational legitimacy including pragmatic, moral and cognitive legitimacy. These three types of legitimacy are tested through analysing four cases in which EU has engaged in sub-Saharan Africa in support of the UN: Operation Artemis (2003), EUFOR RD CONGO (2006), EUFOR Tchad/RCA (2008-2009) and EUFOR RCA (2014-2015). In terms of pragmatic legitimacy, the EU enjoys high level of legitimacy, because these operations served both institutional interests of the EU and self-interests of some member states, particularly France. With regard to moral legitimacy, the EU suffers from a legitimacy deficit. Although declared motives for the launch of these operations was to help the UN in fulfilling its responsibility for the maintenance of international peace and security, indeed, EU engagement in these crisis management operations was to a significant degree driven by the institutional interests of the EU and interests of some individual member states. Moreover, all operations were UN-mandated autonomous EU military operations rather than integrated EU troops in UN-led operations. Thus, real motivation for launching the operations and their modalities undermined moral legitimacy of these operations, because it casted doubts on whether these operations has served the global common good or not. Furthermore, EU’s utilitarian, selective and self-interested use of its crisis management tool puts limit on the EU’s future reliability and taken-for-grantedness as a UN partner in protecting and promoting international peace and security, and thus resulted in cognitive legitimacy deficit.