Although child impulsivity is associated with oppositional defiant disorder (ODD) symptoms, few studies have examined whether family processes moderate this association. To address this gap, we tested whether child-reported family routine moderated the relation between child hyperactivity/impulsivity (HI) and ODD symptoms among a sample of low-income, urban, ethnic-minority children (N = 87, 51% male). Child HI and ODD symptoms were assessed using parent and teacher reports. HI also was indexed by a laboratory task. Family routine was assessed using child self-report. Hierarchical regression analyses indicated that family routine moderated child HI. Among children with higher levels of teacher-reported HI symptoms, lower levels of family routine were associated with higher levels of teacher-reported ODD symptoms compared to children with lower levels of teacher-reported HI symptoms. Children who self-reported higher levels of family routine were rated as low on teacher-reported ODD symptoms, regardless of teacher-reported HI levels. Parent report and laboratory measures of child HI did not produce significant interactions. Lower levels of family routine may confer risk for ODD symptoms among low-income, urban, ethnic-minority children experiencing higher levels of HI.