This study investigated the mediating effect of trait aggressivity on the relation between agreeableness and alcohol-related aggression in a laboratory setting. Participants were 116 healthy male social drinkers between 21 and 30 years of age. Agreeableness and trait aggressivity were measured using the Big Five Inventory and the Buss-Perry Aggression Questionnaire, respectively. Following the consumption of an alcohol or no-alcohol control beverage, participants completed a modified version of the Taylor Aggression Paradigm, in which electric shocks were received from and administered to a fictitious opponent during a competitive task. Aggression was operationalized as the proportion of the most extreme shocks delivered to the fictitious opponent under conditions of low and high provocation. Results indicated that lower levels of agreeableness were associated with higher levels of trait aggressivity. In turn, higher levels of trait aggressivity predicted extreme aggression in intoxicated, but not sober, participants under low, but not high, provocation. Findings highlight the importance of examining determinants of intoxicated aggression within a broader theoretical framework of personality.