Today, the field of international politics, moving away from reductionist frameworks and the emergence of a complicated field with known unknowns, chaotic field by unknowables, and a complex field with unknown unknowns, has faced the dilemma of explaining international phenomena. On this basis, the research attempts to answer the question of what is the tool for explaining changing phenomena in international politics? In response to the research question, it is assumed that complexity theory, by utilizing new connectionist methods, attempts to understand issues in a complex and changing world. Basically, with the development of complicated, complex and chaotic issues in international politics, researchers need to apply complexity theory. This research distinguishes between general systems theory and complexity theory, and also discusses the benefits of complexity theory in social research, and explains international issues as a case study. The research results indicate that complexity theory, with its adaptive insight and irreducibility and irreversibility approach to issues in the field of international politics, is capable of explaining issues in this field.