This article explores the effect of student engagement on learning outcomes associated with students' participation in Model United Nations. We developed an objective assessment of learning outcomes by fielding a survey to conference participants and measuring their general knowledge of the United Nations. We follow-up the survey by asking faculty advisors to report on student outcomes and on the level of activity of Model UN student groups. As predicted by previous research, expectations established by a supportive peer group provide a powerful incentive for student learning, even exceeding the influence of formal instruction in a dedicated credit-bearing course.