Objective: To analyze the root cause of occurrences of severe intoxication in children and adolescents from the perspective of sentinel events. Methods: Observational, retrospective, and qualitative study of a series of cases of seven children and young people with a confirmed clinical picture of intoxication by various agents, treated in a stabilization room of emergency care units or intensive care, and notified to toxicological information and assistance center from January to June 2019. The epidemiological surveillance of sentinel events was used based on a review of hospital documents and in-depth interviews with family members. The Root Cause Analysis (RCA) matrix was used to evaluate the cases and the systematic reconstruction of the cases' antecedents.Results: The age profile of the study population, the pattern of agents and substances involved - poisoning by intentional ingestion in five (71%) cases, indicated critical points and missed opportunities for prevention. The individual and family history analysis indicated as direct causal factors the deviations from norms for preventing poisoning at home or in the family context for all cases.The prevention and health promotion activities in the health services constituted the underlying causes of the occurrences.Conclusion: The root cause analysis identified a deficiency in public policies, but the interface between education, public security, social assistance, economy, and health policies would be preponderant for preventing childhood and youth poisoning.