Introduction. The article is devoted to the issue of searching prerequisites for formation of postnonclassical psychology in the theory of H. Münsterberg. The purpose of the research is to analyze the foundations of H. Münsterberg's psychological system in the context of main criteria of postnonclassical science. Materials and Methods. The article is based on original H. Münsterberg's works, literature devoted to the analysis of his views and the phenomenon of postnonclassical science. The analytical and comparative-historical methods were employed. Results. The author proposes that development of Münsterberg's views can be represented as the transition from classical ("causal") to postnonclassical ("purposive") psychology. It is also stated that the final version of Münsterberg's psychology possesses numerous characteristics of postnonclassical science such as orientation to the historical sciences, treatment of man as a subject, relying on epistemological constructivism, special attention to the axiological features of science, interdisciplinarity, attention to the process of development/self-development, emphasis on the selection function of mind and the acknowledgement of the importance of applied forms of the science. Conclusions. In conclusion, the author states that scrutiny of theories preceding to the mature postnonclassical psychology is important in the context of the further critical analysis of its foundations. In particular, the analysis undertaken in this article indicates that the basis of postnonclassical psychology is idealistic psychology.