To date, most discussion of security privatization in international politics has been focused on the role of private military companies and mercenaries. This article seeks to shift the focus away from the battlefields and toward the less spectacular privatization and globalization of commercial private security. Drawing on Saskia Sassen's notion of state “disassembly,” we situate the growth of private security within broader shifts in global governance. Pointing to the weakness of seeing the rise of private security as an erosion of state power and authority, we show instead a re-articulation of the public/private and global/local distinctions and relationships into what we term “global security assemblages.” Analyzing the role of private security in two such assemblages in Sierra Leone and Nigeria, we show how a range of different security agents and normativities interact, cooperate and compete, to produce new institutions, practices and forms of security governance. Global security assemblages thus mark important developments in the relationship between security and the sovereign state, structures of political power and authority, and the operations of global capital.