BackgroundTriage refers to the process of patient prioritisation in the emergency department (ED). This is based on the severity of the patient’s illness and is performed by emergency nurses (ENs). This has a pivotal role in ensuring patient safety and in ensuring that the ED operates smoothly – so continuous and accurate training are essential. As Emergency Nursing has been formally established in Greece since 2019, it is of the uppermost importance that all Greek ENs should be trained in the use of a standardised triage system. The present study aimed to evaluate the effect of triage training of ENs in the use of the Swiss Triage System (STS) after an intervention of one week.MethodsThe effect of triage training was studied experimentally by comparing performance before and one week after training. A sample of thirty-six ENs from the University Department of Emergency Medicine at AHEPA University Hospital took part. The role of training in triage by the STS was assessed by completing the same self-administered questionnaire before and after a 45-minute e-learning program (presentation video of STS but with simulation scenarios) which was available during the period of a week. The post-training test was taken 2 weeks later, after the training process.ResultsThe most promising finding was that there was a significant improvement in the number of correct answers after the training in triage (p<0.001). A significant improvement was also detected (p<0.001) in the questions that tested vigilance in providing safe health services by ENs, whereas there was no significant association between the number of correct answers and years of emergency experience or level of education, - either before or after the intervention.ConclusionsTriage training seems to successfully improve effective and efficient triage. To the best of our knowledge, this is the first study that has demonstrated that triage training has a significant positive impact on triage performance by ENs in Greece. It is planned to support these findings by real time studies in an ED.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12873-023-00827-5.