This exploratory, descriptive and prospective study aimed to identify the degree of adherence to psychopharmacological treatment of patients who were discharged from psychiatric hospitalization and their knowledge about their prescription and diagnosis. The study was carried out at a Mental Health Service. The sample consisted of all service clients who were discharged from psychiatric hospitalization in the data collection period. A Sociodemographic Questionnaire and the Morisky-Green Test were the instruments used. Data were analyzed through central trend measures. In total, 48 patients participated in the study. Regarding adherence, 70.8% of them showed a low adherence level to psychopharmacological treatment. Moreover, only twenty-one patients knew what their diagnosis was and most did not know or partially knew the name and dose of all prescribed medications.