INTRODUCTION: The healthcare system is complex and dynamic, and the implementation of information technology is seen as an important aid to patient safety. Data reveal that 1 in every 10 patients in developed countries is affected by a clinical error. The transfusion process involves several stakeholders and multiple stages with various critical points within the hospital. This study aims to understand patient safety incidents caused by failures in the Electronic Transfusion Safety System (ETSS) based on barcode technology in a hospital setting, from storage to the administration of blood components to the patient. METHODS: A retrospective study spanning 3 years (2021-2023) with a mixed-methods approach was chosen. A Focus Group with six experts was conducted, and 136 reports from the anonymized incident reporting database with the typology "Blood and Blood Products" from a hospital in Lisbon were analyzed. RESULTS: The ETSS diagram using barcodes allowed for the identification and description of all stages and their stakeholders. The critical points identified were patient identification, multiple relabeling, and transportation. A higher incidence rate of near-miss events was observed during sample collection and prescription. DISCUSSION: This ETSS is hybrid, meaning that it has both human and technological components. Since 96% of the incidents did not cause harm to the patient, error detection and prevention mechanisms are being activated. This study has demonstrated the importance of IT in the transfusion process, as well as the relevance of continuous investment and the involvement of all stakeholders for a better patient safety environment.