Rates of alcohol use peak during the transition from adolescence to young adulthood, a developmental phase that encompasses heightened stress and emotion regulation demands. This mixed methods study examines the influence of a critical developmental transition, high school graduation, on the relationship between problem alcohol use and emotion regulation. High school seniors (N = 117) were surveyed within three months of graduation. Quantitative analyses show that transition stress, but not emotion regulation, predicts alcohol-related problems. Qualitative analyses reveal that adolescent high-risk drinkers engage in a variety of strategies to regulate distress. Implications for adolescent substance misuse prevention programs are discussed.