This article examines the institutional development and evolution of the Shanghai Cooperation Organization (SCO) from 2001 to the present day. The authors identify and characterize the stages and milestones of the organization’s development, while also examining the SCO’s regulatory framework and organizational structure. It is shown that the modern organizational structure of the SCO, formed through a process of long and contradictory evolution, includes a number of subsystems that, along with its fundamental principles of activity, ensure the SCO’s viability and development in the future. Indirect thematic content analysis of 120 official SCO documents shows the main trends of the SCO’s activities, the nature of the organization’s evolution and, ultimately, the stages of its institutional development. The first stage (2001-2004) is associated with the organization’s institutional formation, while the second stage (2004-2008) is characterized by intensive promotion and the minimal complexity of trade, economic, humanitarian and cultural initiatives. The third stage (2008-2014) shows a slight weakening of the impetus for the SCO’s development, while the fourth stage (since 2015) is associated with an attempt to bring the SCO to a qualitatively new level, demonstrating an increase in the efficiency of cooperation in all spheres. A quantitative content analysis of the frequency and dynamics of the use of representative keywords in one of the types of official documents of the SCO (declarations adopted following the summits of the heads of the member states) has made it possible to substantiate a thesis about the gradual complication, detailing, and specialization of the SCO’s activities, as well as to identify and characterize its priorities. In general, the content analysis shows that the SCO has gone through several stages in its development, characterized by qualitative specifics, while maintaining a clear priority on security issues, reflecting the significance of traditional and new threats. A conclusion is reached about the functioning of multilevel interaction on the SCO platform to ensure regional security and cooperation while simultaneously developing both multilateral (including with external actors) and bilateral formats: this indicates the formation of a new model of regionalism in an emerging multipolar world.