Using the actor–partner interdependence model, we examined whether adolescent's agreeableness, best friend's agreeableness, and the interaction between adolescent-friend agreeableness are important for interpersonal functioning. Adolescents (N = 158) in fifth to eighth grades who were part of best friend pairs completed personality and friendship measures. Adolescents' adjustment and victimization experiences were assessed by peer nominations. For boys, best friend's agreeableness moderated the relationship between the target boy's agreeableness and overt victimization, relational victimization, and externalizing problems. For girls, best friend's agreeableness moderated the relationship between the target girl's agreeableness and internalizing problems and prosocial skills. This study provides an initial glimpse into how traits of friends can influence outcomes beyond what would be expected from adolescents' personality alone.