Behavioral economic theories of substance abuse posit that deficits in substance-free reward increase risk for substance misuse, but little research has examined potential moderators of this relationship, including dispositional risk factors. Here, we tested the hypothesis that young adult heavy drinkers with family histories of alcohol misuse would show a stronger association specifically between low evening substance-free reinforcement and alcohol problems compared to those without a family history of alcohol misuse. Participants were 317 college students reporting heavy episodic drinking (M¬age = 18.8, SD = 1.1, 61% female, 79% white) who completed a questionnaire about engagement and enjoyment in rewarding activities not involving substance use after 7pm, along with measures of personal and parental alcohol use/problems. Evening substance-free reinforcement was negatively associated with typical drinking level for women, but not for men. Family history status did not show a significant association with typical alcohol consumption or evening substance-free reinforcement (operationalized as activity participation x enjoyment), but did show a significant association with alcohol problems. Evening substance-free reinforcement was significantly negatively related to alcohol problems for both men and women. However, the presence of a family history of alcohol misuse moderated this relationship, such that only individuals with familial risk for alcohol misuse who reported lower evening substance-free reinforcement evidenced greater alcohol-related problems. These findings suggest that lower evening substance-free reinforcement is associated with alcohol misuse among young adults, and that this association is exacerbated among individuals with familial risk for developing alcohol problems.