Medication nonadherence constitutes a major problem in adolescent psychiatry. Previous studies have identified various factors associated with nonadherent behavior. The aim of this study is to explore adolescents' health beliefs and subjective perceptions relating to psychotropic medication, and to statistically link these to reported medication adherence. The findings presented in this study are part of the multicenter SEMA study (Subjective Experience and Medication Adherence in Adolescents with Psychiatric Disorders). Patients 12-18 years of age were included, who had been treated with a psychotropic medication for at least 2 weeks. The validated MARS (Medication Adherence Rating Scale) and the QATT (Questionnaire on Attitudes Toward Treatment) were used to measure adherence, and a qualitative semi-structured interview was conducted to examine patients' subjective experiences and perceptions. A conventional content analysis was conducted, and Fisher's exact tests were performed to analyze group differences between completely adherent and not completely adherent patients. A total of 64 patients were included in the study. 40.6% (n = 26) were classified as not completely adherent. Distribution patterns of answers to 7 out of 64 questions showed statistically significant group differences between completely and not completely adherent patients. Patients with lower adherence reported the following: feeling worse after taking medication; a lower sense of self-efficacy concerning the improvement of their symptoms; a less trustful physician-patient relationship; a worsened attitude toward medication after experiencing adverse events/"side effects"; less support from their relatives; and fewer individuals in their family who were fully informed about their condition. To our knowledge, this is the first interview-based study to investigate subjective experiences and health beliefs of adolescents with psychiatric disorders and to correlate these findings with rates of medication adherence. The study results will be useful for the development of tools and approaches to increase medication adherence, for example, psychoeducation programs and personalized treatment concepts.