This study evaluated a mechanism by which men’s self-efficacy to intervene increases their likelihood of preventing a laboratory analogue of sexual aggression (SA) via specific verbalizations and whether alcohol inhibits this mechanism. A sample of 78 male peer dyads were randomly assigned to consume an alcoholic or nonalcoholic beverage and complete a laboratory paradigm to assess bystander intervention to prevent SA toward a female who had ostensibly consumed an alcoholic or nonalcoholic beverage. Participants’ verbalizations during the task were subjected to quantitative analysis. Regardless of alcohol use, bystander self-efficacy increased the likelihood of successful bystander intervention via participants’ use of more prosocial verbalizations. Findings highlight prosocial verbalizations within the male peer context that may effectively prevent SA.