This chapter focuses on the role of International Policy Networks (IPNs) in security community building, something which the scholarly community has so far largely ignored. It argues that IPNs play an important role as building blocks of transition from the nascent to the ascendant phase, during which state elites and civil societies are expected to be involved in the densifying patterns of amity and trust. IPNs fulfil four functions: producing knowledge on regional peace, diffusing the norms of self-restraint, influencing security community policies and providing organizational flexibility. The argument is illustrated in an autoethnographic account of the Partnership for Peace Consortium of Defence Academies and Security Studies Institutes (PfPC) and in particular its study group on Regional Stability in Southeast Europe. The chapter theorizes the role of IPNs in the process of security community building and explains methodology.