Abstract: The subject of the study is the mutual influence of discourse deformations and cognitive mechanisms of mentalization and conceptualization of the world in a borderline personality. The aim of the work is to prove the decisive role of the deficits and defects of the "theory of mind" in the development and structuring of the borderline personal organization. The research methodology is represented by interdisciplinary categorical-genetic analysis and synthesis of theories and ideas of phenomenology, cognitive psychology, clinical psychology, psychotherapy, discourse analysis. The author examines the interaction of discursive and cognitive mechanisms of personality in the construction and personalization of the conceptual sphere and "theory of mind". The role of splitting in the conceptualization of reality and the connection of violations of mentalization with changes in the concept of Self are shown. A special contribution of the author to the study of the problem is the systematization of violations of mentalization as predictors of the development of borderline personal organization. The novelty of the research lies in determining the double determination of distortions of the conceptual sphere in the borderline personality by its discourse. Violations of conceptualization processes are described. The systematic organization of the operational units of the mental lexicon, memory and the conceptual sphere in their connection with discourse is determined. The main conclusion is the proof of the relationship between stereotypical discursive formulas, mental vocabulary, methods and abilities of the subject to process information and construct the conceptual sphere. The range of the subject's capabilities in this area is manifested in his discursive formulas of interpretations, assessments, self-regulation. The deformations of these phenomena and the deep rooting of discourse in the structures of thinking correlate with the formation of a pathological "theory of mind" and personal organization. The "borderline" conceptual sphere and the discourse "speaking" by the subject hinder reflection, honest internal dialogue, criticism of representations of reality and support the status quo of the pathology of cognition of reality and orientation in it. The study of the subject's speech models and the understanding of the cognitive-discursive mechanisms of his orientation in his Self and relationships has practical significance in the diagnosis of borderline personality organization and psychocorrective effects on it.