The effects of pubertal timing and adolescent dating on trajectories of depressed mood from early adolescence to young adulthood were examined among youths who participated in the National Longitudinal Study of Adolescent Health. Results showed that for both boys and girls, the trajectories of depressed mood between the ages of 12 and 23 took an inverse U-shape with its peak in mid-adolescence. Furthermore, pubertal timing was a significant predictor of depressed mood at age 12. The pubertal timing effect was nonlinear, suggesting that at age 12, early and late maturing youths were at risk of experiencing elevated levels of depressed mood. The adverse effect of off-time maturation gradually dissipated over time. Moreover, in early adolescence, teenagers, particularly girls, were adversely affected by dating, and off-time physical maturation exacerbated the negative effects of dating. However, the interactive effect of dating and pubertal timing gradually decreased with age. Our findings underscore the importance of examining junctures of biological and social challenges in adolescence to gain better understandings of young people's emotional experiences over time.