Attention-deficit/hyperactivity disorder (ADHD) symptoms and aggressive behaviors are both associated with peer rejection, but little is known the nature of this association with respect to the two symptom dimensions of hyperactivity-impulsivity and inattention and different types of aggression. The present study examines the relations between dimensions of ADHD symptomatology, proactive and reactive aggression, and peer rejection in adolescence. Teacher-reported data were obtained for 200 high school students (grades 9–12; 48 % female; predominately Latino). In structural equation modeling path analyses, the indirect effects of reactive aggression accounted for the link between hyperactivity–impulsivity and peer rejection. Within the same model, neither inattention nor proactive aggression were associated with peer rejection. These findings suggest that reactive aggression may be a key mechanism through which hyperactive–impulsive behavior is associated with peer rejection. Future research and intervention efforts should address the role of reactive aggression among youth with ADHD symptomatology.