Recently, more attention has been devoted to understanding how stressful life events might relate to proactive and reactive aggression. Findings suggest that stressful life events are more strongly linked to reactive, than proactive, aggression; however, it is unclear whether the impact of stressful life events on proactive and reactive aggression might vary as a function of the level of exposure to or type of stressful life event. The current study examined how level of exposure to stressful life events (i.e., witnessed, experienced, and learned about) and stressful life event types (i.e., war zone exposure, sexual victimization, interpersonal violence, and other trauma exposure) related to proactive and reactive aggression. The sample was comprised of 500 undergraduate students (M = 18.96, SD = 1.22, 49.6% male) recruited from a Midwestern university. Findings indicated that all three levels of stressful life event exposure (i.e., experienced, witnesses, and learned) were associated with reactive aggression; however, only witnessed stressful life events were associated with proactive aggression. Clinical implications and future directions are discussed.