Abstract: The article is devoted to one of the most nettlesome issues, i.e. how to teach teenagers with slight mental retardation to differentiate their emotions. This is a very important social issue because teaching such children how to deal with their emotions is the must for harmonic integration of these teenagers into the social environment and society in general. Music therapy is one of a very good means of the development of emotional sphere. The musical language is the language of emotions and feelings, through which music conveys the content and strength of a person's feelings, thereby causing a reciprocal emotional experience. As indicators of the differentiation of emotions, the ability to differentiate emotions through facial expressions was measured using pictograms and photographs, and the verbal designation of emotions was also evaluated. The study showed that adolescents with a mild degree of mental retardation experience pronounced difficulties in identifying emotions, do not take into account emotional nuances. The positive influence of the means of music therapy on the ability to differentiate emotions, increase the accuracy and diversity of expression of their own emotions is proved. The musical impact allowed adolescents with a mild degree of mental retardation to expand the range of emotions experienced, to increase the emotional vocabulary.