This thesis examines the causal factors surrounding the different, and somewhat antithetical, outcomes in the African Union (AU)’s international security partnerships with the European Union (EU), the United Nations (UN), North Atlantic Treaty Organization (NATO) and the United States Africa Command (US AFRICOM). Typically, the literature on partnership posits that conjoined partnerships should lead to value addition. This was the assumption when the AU signed different partnership agreements with these organizations—that, these would lead to an effective operationalization of the African Peace and Security Architecture (APSA), which is the flagship project for African regional security. At their height, these partnerships collectively failed to deliver, as the overall outcome was mediocre. This study set out to examine the causal factors behind this grand failure. The thesis is analytically dichotomous, setting out to examine regional as well as inter-regional or trans-regionalism factors in the partnership. At a regional level, it examines the following factors: t did these by examining the following factors in each partnership: the cogency and relevance of African regional security policy; African solidarity and collective diplomacy; and the ductility of African strategic citizenship. At an inter-regional level, the thesis examines the following issues in and across the partnerships: historical precedence and influence; levels of diplomatic engagement; managerial 6 complexity; resource disbursement and directionality—inputs into the APSA project; and preference and interest linkage. In its conclusion, the study holds that the mixed outcomes in the partnerships are mainly an outcome of limited institutionalization of the partnerships. This is a function of the dichotomous factors identified earlier. At a regional level, the limited institutionalization of the partnerships is a function of fuzzy collective diplomacy and strategic citizenship. At an inter-regional level, this is a function of limited or at times skewed diplomatic engagement; contested resource disbursement and directionality and intermittently abstruse preference and interest linkage.