Indicators are used by most organizations to track their safety performance. Research attention has been drawn to what makes for a good indicator (specific, proactive, etc.) and the sometimes perverse and unexpected consequences of their introduction. While previous research has demonstrated some of the complexity, uncertainties and debates that surround safety indicators in the scientific community, to date, little attention has been paid to how a safety indicator can act as a boundary object that bridges different social worlds despite being the social groups’ diverse conceptualization. We examine how a safety performance indicator is interpreted and negotiated by different social groups in the context of public procurement of critical services, specifically fixed-wing ambulance services. The different uses that the procurer and service providers have for performance data are investigated, to analyze how a safety performance indicator can act as a boundary object, and with what consequences. Moving beyond the functionality of indicators to explore the meanings ascribed by different actors, allows for greater understanding of how indicators function in and between social groups and organizations, and how safety is more fundamentally conceived and enacted. In some cases, safety has become a proxy for other risks (reputation and financial). Focusing on the symbolic equivocality of outcome indicators and even more tightly defined safety performance indicators ultimately allows a richer understanding of the priorities of each actor within a supply chain and indicates that the imposition of oversimplified indicators may disrupt important work in ways that could be detrimental to safety performance.