Research has highlighted that some types of mental disorders are associated with widespread discrimination and stigma, phenomena that negatively affect adherence. The aim of the present study was to examine the association between stigma and adherence to pharmacological treatment in patients diagnosed with bipolar mood disorder (BD), attention deficit hyperactivity disorder (ADHD) and schizophrenia (SZ). A total of 112 patients (age range: 20-68 years, Median age = 42.08; SD age = 12.02) from Brazil (38.4% ADHD, 34.8% SZ, and 26.8% TB) participated in the study. Treatment adherence was measured using the Medication Adherence Questionnaire, personal stigma by means of the Internalized Stigma of Mental Illness, Stigma Scale, and Perceived Devaluation and Discrimination Scale, and self-esteem with Rosenberg’s Self-Esteem Scale. Results showed an association between personal stigma and treatment adherence for all three types of disorder. The lower the personal stigma, the higher the adherence to treatment. The study highlights the role of stigma and self-esteem in relation to treatment adherence, with possible implications for future psychotherapy for these disorders.