Social difficulty during adolescence contributes to internalizing problems (e.g., depression, stress) and spurs cycles of aggression and retaliation. In this article, I review how implicit theories of personality—beliefs about whether people can change their socially relevant characteristics—cause some adolescents to respond to social difficulty in these ways while others do not. Believing an entity theory of personality—the belief that people cannot change—causes people to blame their own and others’ traits for social difficulty, and predicts more extreme affective, physiological, and behavioral responses (e.g., depression, aggression). Interventions that teach an incremental theory of personality—the belief that people can change—can reduce problematic reactions to social difficulty. I discuss why interventions to alter implicit theories improve adolescents’ responses to conflict, and I propose suggestions for research.