The paper focuses on the use of psychological training as a method of developing assertiveness in adolescents. The theoretical basis for this study was found in the ideas of L. Vygotsky, T. Dragunova and D. Elkonin. The main phenomenon investigated in the empirical part of the research is the influence of socio-psychological training on the practical skills of confident behaviour in teenagers, their ability to openly and directly formulate and discuss their goals and strive towards achieving them while maintaining friendships and partnerships with others, personal health and energy. To test the hypothesis in the course of the study, before and after the sociopsychological training the authors used the following psychodiagnostic methods: “Investigation of the level of personal self-esteem”, “The Dembo-Rubinstein Ladder”, Spielberger’s “Investigation of the level of anxiety”, and Leonhard’s “Investigation of character accentuation”. The study was conducted in 2018 in a secondary school in the town of Gatchina. The outcomes of the study confirmed that socio-psychological training (SPT) can be used as a method of generating sound self-esteem in adolescents. Significant positive differences between the indicators of self-esteem and the emotional sphere in the experimental group before and after the training support the idea that SPT conducted in order to correct adolescent self-esteem was effective. After the training the students perceived themselves as more attractive, sociable, less conflicted, they recognized themselves as good friends; showed less aggression and anxiety, their self-esteem gained adequacy, they became calmer, more balanced, in other words, assertive. Following the training, the vast majority of the subjects showed behaviour within the limits of low situational anxiety. It can be assumed that after the training they were able react fairly calmly to personal problems. The high level of emotional imbalance exhibited by the subjects prior to the training allows the authors to suggest that the teenagers were prone to mood swings and bouts of weak will, sought trills and new sensations and were inclined towards laziness and dalliance. The results of the conversation with the teenagers after the training suggest that the adolescents reached a mature understanding of such concepts as “conflicting”, “balanced”, “quick-tempered”, “sociable”, and “a good friend”. However, the concept of “attractive” was still somewhat misinterpreted by them as merely a description of an individual’s “beauty” meaning their good looks.