The aim of the study was to examine the effect of music therapy on self-esteem improvement in a 29-year-old young woman with mild intellectual disabilities. The examinee is a member of the Korablja Association. The research was conducted in form of a case study and consisted of 8 sessions: one session per week, led by a music therapy student (the examiner). Before the first session, a group of experts from the Korablja Association assessed the emotional development (SED scale; Došen, 1997). Before the first and after the last session, the examiner conducted an adjusted Coopersmith Self-Esteem Inventory (SEI; Coopersmith 1967) and a Rosenberg Self-Esteem Scale (RSE; Rosenberg 1989). The primary method was writing a song, while the accompanying methods and techniques included improvisation, receptive music therapy and musical executive function training. The song writing method is a process completed by a public performance in which the examinee and the examiner sing a song. The Coopersmith inventory had more confident answers after the music therapy (56) than before the music therapy (48), and the total number for all scales increased by 8. The Rosenberg scale provided the same result before and after music therapy. In the last session, after the song was performed at Korablja Association, the examinee completed the survey, which represents a quality contribution to the study. The results showed that the music therapy has made some positive contribution to the examinee’s increase of the self-esteem.