Objective: To explore the effects of social exclusion on reactive aggression in middle school students and to examine the mediating role of emotional sensitivity. Methods: The Reactive Proac-tive Aggression Questionnaire, the Emotional Reactivity Scale, and the Adolescent Social Exclusion Scale were selected to test 351 middle school students. Results: Social exclusion was significantly and positively correlated with reactive aggression in middle school students, and emotional sensi-tivity played a fully mediating role in the effects of social exclusion on reactive aggression in middle school students. Conclusion: Social exclusion positively predicted reactive aggression in middle school students, and emotional sensitivity was a full mediator between social exclusion and reactive aggression in middle school students.