Friendships assume a salient role in well-being during mid-adolescence. This research examined (a) how friendship quality (stressful vs. supportive) is differentially associated with mid-adolescents' social adjustment (engagement in antisocial vs. prosocial behavior); (b) the extent to which these associations are contingent on individual differences in the tendency to base one's self-worth on peer approval; and (c) whether these associations differ in boys and girls. Adolescents (N = 324; 179 girls; M[subscript age] = 14.87; SD = 1.22) completed questionnaires during a school-based assessment. For boys, friendship stress was associated with more antisocial behavior among adolescents with high levels of avoidance-oriented need for approval (NFA), whereas friendship support was associated with more prosocial behavior among adolescents with low levels of avoidance-oriented NFA. For girls, friendship quality and NFA made independent contributions to social behavior. This research provides a more nuanced understanding of the role of friendship quality in social competence.