Adolescent peer aggression is a well‐established correlate of romantic relational aggression; however, the mechanisms underlying this association are unclear. Heavy episodic drinking (or “binge” alcohol use) was examined as both a prior and concurrent mediator of this link in a sample of 282 12–18 year old interviewed four times over 6 years. Path analyses indicated that early peer relational and physical aggression each uniquely predicted later romantic relational aggression. Concurrent heavy episodic drinking fully mediated this effect for peer physical aggression only. These findings highlight two important mechanisms by which peer aggression may increase the risk of later romantic relational aggression: a direct pathway from peer relational aggression to romantic relational aggression and an indirect pathway through peer physical aggression and concurrent heavy episodic drinking. Prevention programs targeting romantic relational aggression in adolescence and young adulthood may benefit from interventions that target multiple domains of risky behavior, including the heavy concurrent use of alcohol. Aggr. Behav. 42:563–576, 2016. © 2016 Wiley Periodicals, Inc.