Social contextualist analysis, by contrast to much of the existing research on international negotiations, emphasizes the social and organizational environment in which negotiations take place and the effect that it can have on the decision-making of participants. This paper applies a social contextualist lens to negotiations held to decide upon the form and function of the African Peace and Security Architecture (APSA). Certain elements of the Architecture, which is one of the central pillars of the African Union (AU), present something of a puzzle for theorists, given the cession of sovereignty they represent on a continent where leaders have traditionally been very protective of their authority. After illustrating the limited value of the most prominent approaches to negotiation analysis, the social contextualist framework is outlined. The analysis incorporates negotiations held to decide upon a number of features of APSA. Its findings rest upon interviews conducted with representatives from AU member states and AU officials, as well as examination of a broad range of primary and secondary documents. In highlighting the significance of factors that are generally overlooked by traditional approaches, a case is made for greater consideration of social contextual factors in analysis of international negotiations.