The Triage process is a crucial process of Emergency Departments, and scholars have proposed several solutions to streamline the processing of patients and reduce the waiting time of more urgent ones. However, a not thoroughly investigated issue concerns the factors influencing the decision-making performed by the nurses in the assignment of Triage’s priority code. The Triage decision-making is a dynamic and complex process: the decision emerges after an interpretation process of patient clinical conditions influenced by the interaction of organizational rules and environment conditions with nurse’s experience and beliefs. We investigate the Triage process through the fuzzy Qualitative Comparative Analysis (QCA). QCA is a method used to test theory-based conditions considering multiple interrelated variables that lead to the same outcome. More specifically, we show how the QCA allows researchers to figure out how the interaction between individual, organizational, environmental factors affect the Triage decision-making. This analysis will enable us to suggest some possible interventions to improve the Triage process. This research has been performed through direct observation of the Triage carried out in an Emergency Department of a Hospital located in the South of Italy.