Since its establishment in 2001, The Shanghai Cooperation Organization (SCO) has gradually increased its influence and importance while becoming an independent venue for the Central Asian states to manage regional and national security. The SCO focuses on a new type of (non-traditional) security, and its diverse membership differentiates it from other security institutions. In particular, and uniquely, the SCO has impacted the national security identities of its members. The processes examined in this paper are not easily reconciled with traditional state-centric security paradigms or the dominant strategic discourse. Thus, recourse must be had to analytical tools provided by social constructivism and, to a lesser extent, English School rationalism. The paper proposes a revised model of socialization with acculturation as a central mechanism and applies it to the security identity formulation of four Central Asian Republics in order to explain the shifts in the security discourses at both the national and regional levels.