--- - |2 An emerging body of research suggests that telomere length (TL)—a measure of cellular aging—is inversely associated with experiences of childhood stress. Given the salience of peer relationships in childhood and adolescence, we tested whether relational victimization is a unique and specific predictor of salivary TL in girls. Results examining 122 girls (ages 9–15) revealed that greater relational victimization was related to shorter TL but that similar associations were not evident for other measures of social relationships nor accounted for by factors related to depression, life stress, or 5‐HTTLPR genotype. The present findings suggest that relational victimization is uniquely associated with TL in adolescence, revealing a link between key aspects of social relationships and biological processes. - Journal of Research on Adolescence, EarlyView.