This 20-year longitudinal study showed that the young adult offspring of teen mothers are atrisk for a range of adverse outcomes including early school leaving, unemployment, earlyparenthood, and violent offending. We tested how much the effect of teen childbearing onoffspring outcomes could be accounted for by social selection (in which a woman'scharacteristics that make her an inadequate parent also make her likely to bear children in herteens) versus social influence (in which the consequences of becoming a teen mother also bringharm to her children, apart from any characteristics of her own). The results provided support forboth mechanisms. Across outcomes, maternal characteristics and family circumstances togetheraccounted for approximately 39% of the effect of teen childbearing on offspring outcomes.Consistent with a social-selection hypothesis, maternal characteristics accounted forapproximately 18% of the effect of teen childbearing on offspring outcomes; consistentwith a social-influence hypothesis, family circumstances accounted for 21% of the teenchildbearing effect after controlling for maternal characteristics. These results suggest that publicpolicy initiatives should be targeted not only at delaying childbearing in the population but atsupporting individual at-risk mothers and their children.