Impulsivity is strongly related to the development of adolescent substance use. Therefore, understanding factors that influence impulsive characteristics is important for the development of prevention and intervention programs. Intervention and prevention programs focused on factors that influence impulsive characteristics are especially important for those at particularly high risk for the expression of impulsivity - those with a family history of substance use disorder. A factor of particular interest is family functioning. AIM To examine family functioning as a mediator of relations between having a family history of substance use disorder and impulsivity. METHODS Participants included a majority Hispanic sample of pre-adolescent boys and girls (mean age 10.99, SD = .84) recruited from the community who did (FH+) and did not (FH-) have a family history of substance use disorder. FH status and the quality of family functioning were compared at the initial visit with impulsiveness assessed a year later. RESULTS Results showed FH+ children had worse family functioning; worse family functioning was related to higher levels of impulsivity, and higher levels of impulsivity among FH+ children were due to the influence of family functioning on levels of impulsivity. In other words, family functioning mediated relations between having a family history of substance use disorder and impulsivity. CONCLUSION These results indicate that higher levels of impulsivity in FH+ children are due in part to worse family functioning.