This study examined how impulsivity moderates the relationship between sexual abuse and substance use frequency in a large international sample. Participants (N = 64,472) completed the Alcohol, Smoking, and Substance Involvement Screening Test (ASSIST-11), the UPPS-P Impulsive Behavior Scale, and sexual abuse measures through the International Sex Survey. Structural equation models tested associations between childhood sexual abuse (CSA), adolescent/adult sexual abuse (AASA), and combined exposure with substance use frequency, and explored moderation by impulsivity across gender identity, sexual orientation, and country. AASA and CSA+AASA were consistently associated with higher substance use frequency, while CSA alone showed weaker or inconsistent associations across groups. Urgency and premeditation facets of impulsivity moderated these associations, particularly among sexual and gender minority individuals. Country-level differences indicated cultural and contextual variation in how impulsivity interacts with trauma to influence substance use. Findings underscore the need for targeted, culturally responsive interventions addressing impulsivity in the aftermath of sexual trauma.