While children born at extremely low birth weight (ELBW; <1000 g) are at elevated risk for peer victimization, no research has examined its effects on mental health in adulthood. ELBW survivors and matched normal birth weight (NBW; >2500 g) controls were part of a prospective, population-based study in Ontario, Canada. Peer victimization before age 16 was self-reported at age 22 to 26 years by using a 10-point measure. Presence of psychiatric disorders was examined at age 22 to 26 years (ELBW n = 142, NBW n = 133) and age 29 to 36 years (ELBW n = 84, NBW n = 90). After adjustment for confounding variables, for each 1-point increase in the peer victimization score, ELBW survivors had increased odds of current depressive (odds ratio [OR] = 1.67, 95% confidence interval [CI], 1.23-2.28), anxiety (OR = 1.36, 95% CI, 1.05-1.76), avoidant (OR = 1.39, 95% CI, 1.08-1.79), antisocial (OR = 1.92, 95% CI, 1.06-2.87), and attention-deficit/hyperactivity (OR = 1.39, 95% CI, 1.06-1.83) problems at age 22 to 26 years. At age 29 to 36 years, peer victimization score predicted increased odds of current panic disorder (OR = 1.69, 95% CI, 1.01-2.83) and obsessive-compulsive disorder (OR = 3.56, 95% CI, 1.25-10.09). For NBW controls, peer victimization predicted increased odds of antisocial problems at age 22 to 26 years. ELBW survivorsand NBW participants are vulnerable to the adverse psychiatric effects of childhood peer victimization in adulthood.