International security cooperation usually takes one of two forms. A classical collective security organization is designed to promote international security through regulating the behavior of its member states. A defensive security organization is designed to protect a group of states from threats emanating from a challenging state or group of states. Both forms of security cooperation bind states to act in concert with respect to threats presented by other states. The emergence of non‐state actors such as terrorist or extremist organizations challenges traditional forms of collective security. Threats from political extremism, terrorism, and outlaw organizations have grown in visibility during the past decade in the countries of Eurasia. The terrorist attacks of September 11 and the ensuing global war on terrorism have given added impetus to the Eurasian inter‐state cooperation in confronting non‐traditional threats and challenges from non‐state actors. Bearing in mind the theory of collective security, this article analyzes threats posed by non‐state actors with respect to Eurasian collective security organizations including the Shanghai Cooperation Organization, the Conference on Interaction and Confidence Building Measures, and the CIS Collective Security Treaty Organization. The article concludes that the effectiveness of these organizations at achieving stated objectives depends upon their capacity to adopt new criteria of effectiveness.