ABSTRACTObjectives:to analyze the incidence of preventable adverse events related to health care in adult patients admitted to public hospitals in Brazil.Methods:observational, analytical, retrospective study based on medical records review.Results:medical records from 370 patients were evaluated, 58 of whom had at least one adverse event. The incidence of adverse events corresponded to 15.7%. Adverse events were predominantly related to healthcare-related infection (47.1%) and procedures (24.5%). Regarding the adverse event severity, 13.7% were considered mild, 51.0% moderate, and 35.3% severe. 99% of adverse events were classified as preventable. Patients admitted to the emergency room had a 3.73 times higher risk for adverse events.Conclusions:this study’s results indicate a high incidence of avoidable adverse events and highlight the need for interventions in care practice.