Este artigo está licenciado sob forma de uma licença Creative Commons Atribuição 4.0 Internacional, que permite uso irrestrito, distribuição e reprodução em qualquer meio, desde que a publicação original seja corretamente citada. ABSTRACT AIMS: To evaluate the legal aspects and indicators of rational drug use in prescriptions issued by mental health services. METHODS: Prescriptions dispensed by pharmacies of reference of the Psychosocial Care Centers located in the Medio Paraopeba region, Minas Gerais, Brazil, were evaluated. A semi-structured questionnaire was developed for the collection of data, including the World Health Organization prescribing indicators and the criteria for compliance of prescriptions with the Brazilian legislation. RESULTS: A total of 390 prescriptions were analyzed, and the average number of drugs in each prescription was 2.17. It was observed that 96.78% of the drugs were prescribed by their generic names and that 97.13% were on the essential medicines list of municipalities. Legal aspects of the prescriptions were met for several criteria: 99.23% of the prescriptions had the prescriber's signature, 98.97% showed the date of issue, and 97.69% contained minimum information for the user regarding the use of the medications. None of the assessed health centers issued prescriptions with all the necessary patient data and with information about the dispensed medications, as required by law. CONCLUSIONS: The study indicated that most of the prescriptions analyzed complied with the legal requirements and that the indicators of rational medication use were satisfactory. However, information on dispensing control and records of users was incomplete, demonstrating problems with patient identification and with the traceability of dispensed medicines.