BackgroundDisaster triage training equips learners with the critical skills to rapidly evaluate patients, yet few medical schools include formal triage training in their curriculum. Simulation exercises can successfully teach triage skills, but few studies have specifically evaluated online simulation to teach these skills to medical students.AimsWe sought to develop and evaluate a largely asynchronous activity for senior medical students to practice their triage skills in an online format.MethodsWe developed an online, interactive triage exercise for fourth-year medical students. For the exercise, the student participants acted as triage officers for an emergency department (ED) at a large tertiary care center during an outbreak of a severe respiratory illness. Following the exercise, a faculty member led a debriefing session using a structured debriefing guide. Pre- and post-test educational assessments used a five-point Likert scale to capture the helpfulness of the exercise and their self-reported pre- and post-competency in triage. Change in self-reported competency was analyzed for statistical significance and effect size.ResultsSince May 2021, 33 senior medical students have completed this simulation and pre- and post-test educational assessments. Most students found the exercise “very” or “extremely” helpful for learning, with a mean of 4.61 (SD: ±0.67). Most students rated their pre-exercise competency as “beginner” or “developing” and their post-exercise competency as “developing” or “proficient” on a four-point rubric. The average increase in self-reported competency was 1.17 points (SD: ±0.62), yielding a statistically significant difference (p < 0.001) and large effect size (Hedges’ g: 1.94).ConclusionsWe conclude that a virtual simulation can increase students’ sense of competence in triage skills, using fewer resources than in-person simulation of disaster triage. As a next step, the simulation and the source code are publicly available for anyone to engage with the simulation or adapt it for their respective learners.