Background: Impulsivity is a strong, consistent risk factor for heavier drinking and internalizing symptoms. However, it is unclear whether certain facets of impulsivity (e.g., lack of premeditation and negative urgency) are differentially related to drinking quantity versus internalizing and whether drinking quantity and internalizing serve as mechanisms through which impulsive traits confer risk for negative alcohol consequences. Method: Data are from a longitudinal study of contextual influences on alcohol response in emerging adults (N = 448, Mage = 22.27, 43.5% female). Longitudinal path models in Mplus tested whether UPPS-P impulsivity facets at T1 were prospectively associated with drinking quantity and internalizing symptoms (T2), and whether T2 drinking and internalizing symptoms mediated effects of T1 impulsivity on T3 negative alcohol consequences. Separate models were tested for positive and negative urgency and sex and age were included as model covariates. Results: Consistent with study hypotheses, T1 lack of premeditation indirectly predicted T3 negative alcohol consequences through heavier T2 drinking, whereas T1 negative urgency indirectly predicted T3 negative alcohol consequences through higher T2 stress and depressive symptoms. Contrary to hypotheses, lack of perseverance was not related to drinking quantity and alcohol use was not prospectively related to alcohol consequences. Conclusions: The current study found that distinct impulsive traits were associated with drinking quantity and internalizing symptoms, both of which conferred risk for negative alcohol consequences. Findings underscore the importance of targeting drinking behavior as well as internalizing symptomology based on the presence of specific impulsive personality traits. Such personality-centered interventions have shown promise in prior research.