This multimethod research linked the Big Five personality dimensions to interpersonal conflicts. Agreeableness was the focus because this dimension is associated with motives to maintain positive interpersonal relations. Converging responses to both hypothetical conflicts and to diary records of actual daily interpersonal conflicts across a two-week period were assessed. Agreeableness was expected to moderate affective responses and tactical choices during conflicts. Patterns of daily conflict were related to self-reported reactions to hypothetical conflicts and to teacher-rated adjustment in adolescents. As predicted, Agreeableness was related to responsiveness to conflict. Agreeableness differences and use of destructive tactics in conflict were significantly related to evaluations of the individual’s adjustment by knowledgeable raters. Among the Big Five dimensions, Agreeableness was most closely associated with processes and outcomes during interpersonal conflict.