Background: Severe transfusion reactions resulting from errors in matching the correct blood with the correct patient are considered never events. Despite the relative technical simplicity of barcode scanning for patient-blood bag matching, the adoption and universal application of this safety measure are by no means universal. This study highlights the logistical and institutional challenges associated with spreading, scaling up, and sustaining such IT-supported safety measures in healthcare. Study Design and Methods: We report findings from a 5-year, prospective, multi-site case study conducted across one hospital in England and three hospitals in the Netherlands. Ethnographic methods, including interviews and observations, were used at each site to investigate the implementation of barcode scanning-supported safety pathways for blood transfusions. Results: Significant variation was observed across the sites in the adoption and implementation of barcode scanning-supported safety pathways. Despite the potential for reducing transfusion errors, the introduction of this innovation was met with varying levels of success in different settings. Discussion: This study highlights the critical role of inter-hospital learning and flexible system design in successfully implementing barcode scanning-supported safety pathways for blood transfusions. A more structured, national-level network for knowledge sharing could enhance the spread and sustainability of such innovations across healthcare settings.