This article explores what leadership practices are associated with International Baccalaureate (IB) student achievement. Using a combined data set of Diploma Program (DP) exam scores and teachers' survey responses about school leadership from 29 schools in Southeast Asia, the article reports certain leadership practices (i.e., strategic resourcing, monitoring classroom teaching and curriculum, encouraging teacher learning and development) exercised in the sampled IB schools that are significantly associated with student academic outcomes. This article contributes to empirical literature on school leadership effects on student learning in international school settings, which is an underresearched inquiry in the field.