This paper examines the relationship between self-esteem in adolescence and later mental health, substance use, and life and relationship outcomes in adulthood. The investigation analyzed data from a birth cohort of approximately 1,000 New Zealand young adults studied to the age of 25. Lower levels of self-esteem at age 15 were associated with greater risks of mental health problems, substance dependence, and lower levels of life and relationship satisfaction at ages 18, 21, and 25. Adjustment for potentially confounding factors reduced the strength of these associations to either moderate or statistically nonsignificant levels. It was concluded that the effects of self-esteem during adolescence on later developmental outcomes were weak, and largely explained by the psychosocial context within which self-esteem develops.