There has been interest in the antecedents and mental health impacts of eating and body image disturbances in adolescence. Less is known about longer-term mental health impacts into young adulthood, as longitudinal studies with data spanning this developmental period are rare. We capitalize on mental health data collected across adolescence and young adulthood from a population-based cohort study that has been following >2000 Australian children and their families from infancy to young adulthood. This sample comprised 1,568 participants who completed the Eating Disorder Inventory drive for thinness and bulimic behavior (the severity of binge-purge patterns) subscales, and a modified version of the body dissatisfaction subscale in mid-adolescence (15-16 years), or the Depression Anxiety Stress Scales in young adulthood (19-20, 23-24, and 27-28 years). After adjusting for baseline demographic and prior mental health factors (<13 years of age), all three indices of eating and body image disturbances in adolescence predicted each mental health outcome in young adulthood. Mental health risks associated with adolescent body dissatisfaction and bulimic behavior scores remained stable across young adulthood, with men having more pronounced problems associated with bulimic behavior scores than women. In contrast, mental health risks associated with adolescent drive for thinness scores diminished across this period similarly for men and women. Findings suggest that adolescent eating and body image disturbances may have long-term mental health impacts that extend into young adulthood. This underscores the need for early preventative intervention, and longer-term monitoring and support for body image and eating disturbances.