Drawing from theory that implicates the peer appearance culture in shaping adolescents' appearance concerns, we examined whether friends' reports of the appearance culture were associated with,increases in emerging adolescents' appearance-based rejection sensitivity (appearance-RS) over six months. Gender and age differences were also assessed. We used peer nominations to identify dyadic friendships (n = 178 adolescents/89 dyads, M-age = 12.0), and unique friendship networks (n = 284, M-age = 12.0). Appearance-RS increased more over a 6-month period when adolescents had reciprocated best friends who reported more body change and extreme weight loss behaviours, and when they had a best friend with a higher BMI. This suggests that observable features of friends may be most relevant. Also, however, adolescents showed greater increases in appearance-RS when they belonged to a friendship group that reported higher appearance dissatisfaction, and adolescents showed less increases in appearance-RS when their friends reported more positive appearance self-perceptions. (C) 2016 Elsevier Inc. All rights reserved.