This study assessed the hypothesis that popularity in adolescence takes on a twofold role, marking high levels of concurrent adaptation but predicting increases over time in both positive and negative behaviors sanctioned by peer norms. Multimethod, longitudinal data, on a diverse community sample of 185 adolescents (13 to 14 years), addressed these hypotheses. As hypothesized, popular adolescents displayed higher concurrent levels of ego development, secure attachment, and more adaptive interactions with mothers and best friends. Longitudinal analyses supported a popularity-socialization hypothesis, however, in which popular adolescents were more likely to increase behaviors that receive approval in the peer group (e.g., minor levels of drug use and delinquency) and decrease behaviors unlikely to be well received by peers (e.g., hostile behavior with peers).