Previous research has shown that adolescent girls tend to resemble their friends in their level of body dissatisfaction and disordered eating. However, no studies to date have attempted to disentangle the underlying peer selection and socialization processes that may explain this homophily. The current study used longitudinal stochastic actor-based modeling to simultaneously examine these two processes in a large community sample of adolescent girls (N = 1,197) from nine Australian girls' high schools. Friendship nominations and measures of body dissatisfaction, dieting and bulimic behaviors were collected across three annual waves. Results indicated that selection rather than socialization effects contributed to similarity within friendship groups when both processes were examined simultaneously. Specifically, girls tended to select friends who were similar to themselves in terms of body dissatisfaction and bulimic behaviors, but dissimilar in terms of dieting. Network and individual attribute variables also emerged as significant in explaining changes in adolescents' friendships and behaviors. As well as having important clinical implications, the findings point to the importance of controlling for friendship selection when examining the role of peers in adolescent body image and eating problems.