Early pubertal timing has been associated with increased alcohol use, drunkenness, and alcohol use disorders in both boys and girls during adolescence. It is not clear, however, whether the effect of early pubertal timing persists into late adolescence and young adulthood, whether its effect differs by gender, and if contextual factors (e.g., peer alcohol use) amplify such effect. This study attempts to address these questions by examining the trajectories of alcohol use and heavy drinking from early adolescence to young adulthood in males and females using data from the National Longitudinal Study of Adolescent Health (Add Health). Results show that for both males and females, early pubertal timing was associated with higher alcohol use and heavy drinking trajectories. These effects persisted into young adulthood and were found to be stronger for males than for females. Moreover, there was a significant interaction effect between friends' drinking and pubertal timing on alcohol use and heavy drinking trajectories; but the interaction effect also differed for males and females. These findings suggest that early pubertal timing is a risk factor for alcohol use and has long-term implication for individuals' health.