The European Union's (EU's) engagement in Africa has long focused on interregional security cooperation with specific Regional Organisations (ROs). Bilateral interregionalism between African ROs and the EU is particularly implemented through cooperation with the Regional Economic Communities (RECs) and the African Union (AU) under the umbrella of the African Peace and Security Architecture (APSA). However, regional groups such as the Multinational Joint Task Force (MNJTF) or the G5 Sahel have emerged as security actors, and as a consequence Africa-EU relations take place beyond the APSA framework. I argue that unintended consequences of these hybrid interregionalisms affect traditional relationships of the EU in West Africa, such as the ECOWAS-EU partnership as bilateral interregionalism. Whereas research has acknowledged the increasing relevance of Africa-EU relations, scholars have so far barely interrogated the unintended consequences of the rather deliberate EU-Africa relations. This contribution seeks to analyse the potential implications that arise from these effects. Based on media data, official documents and expert interviews conducted in Brussels, Nairobi, Addis Ababa and Abuja, I specifically place an emphasis on the EU's engagement in West Africa. The study finds that hybrid interregionalism beyond the APSA as consequence of the enhancement of regional ad hoc groups led to competition, less efficiency and extraversion-approaches applied by African elites as unintended consequences.