The relevance of the published research on the actualization of interdisciplinary integration at mathematics lessons is due to the need for conceptual clarification of what is included in the concept of an academic discipline, and, consequently, interdisciplinary integration. Currently, there is no uniformly consistent interdisciplinary terminology, moreover, interdisciplinary boundaries are often difficult to overcome. In pedagogical practice, intersubject is only rhetorically praised, but its practical implementation is often very difficult. This publication aims at studying the role and potential of the actualization of interdisciplinary integration at mathematics lessons. Mathematics is widely recognized as central to human development. However, there are not enough research concerning teaching mathematics in various contexts of educational systems. The object of the study is interdisciplinary integration at mathematics lessons within the framework of holistic learning concepts. Consideration of interdisciplinary integration at mathematics lessons gives researchers the key to education of the XXI century. Nevertheless, few studies are published concerning the proposed object that can serve as a basis for practice in the actualization of interdisciplinary integration at mathematics lessons. Qualitative critical phenomenology was used as a research methodology, since the logic of the actualization of interdisciplinary integration at mathematics lessons reflects a system of historically determined values transmitted by institutionalized models of behaviour, thinking and speech. The application of critical phenomenology allowed us to come to an understanding of how the social and pedagogical aspects of the actualization of interdisciplinary integration at mathematics lessons affect the ways in which students construct reality. Critical phenomenology has made it possible to identify various approaches to the study of the actualization of interdisciplinary integration at mathematics lessons, to study the impact of social interactions in the construction of interdisciplinary discourse by students, the possible impact that interdisciplinary discourse can have on learning. Since the research was of a qualitative nature, it was inevitably influenced by the interpretative methodological paradigm, which recognizes that individual life experience is formed by context, and ideas about knowledge are socially constructed.