ABSTRACT Objectives: to assess the implementation of a nurse-initiated pain management protocol for patients triaged as semi-urgent, and its impact in pain intensity, in the Emergency Department. Methods: a prospective cohort study for adult patients with pain who had been triaged as semi-urgent and admitted to the hospital’s Emergency Department. Patients who received the intervention (pain-management protocol with analgesic administration) were compared to those who were managed using the conventional approach (physician evaluation prior to analgesic administration). Results: of the 185 patients included, 55 (30%) received the intervention, and 130 (70%) were managed conventionally. Patients in the intervention group were more likely to have taken pain medication in the 4 hours prior to admission, and reported higher levels of pain at admission and more significant reductions in pain level. Conclusions: despite low protocol adherence, the intervention resulted in higher reported pain relief.